docs: add build-doc tooling and a README for every example

Documentation tooling:
- Add the `build-doc` skill and `tools/build_doc.py` wrapper for local
  Sphinx builds (clean / -W / open).
- Enable Markdown (MyST) in conf.py and auto-collect
  examples/{device,host,dual}/*/README.md into a 3-level Examples nav
  (Examples > Device/Host/Dual > example), noting each page's source
  location and normalizing headings to a single H1.
- Remove the stale `.claude/commands/build-doc.md`; point the AGENTS.md
  Documentation section at the skill.

Example docs:
- Add a README.md for every device/host/dual example: what it does, USB
  interface table, notable tusb_config.h settings, generic CMake + Make
  build steps, and how to try it.
- Fold each *_freertos variant into its base README, noting the FreeRTOS
  source path and any RTOS-specific behavior.

Generated docs/examples/ output is git-ignored. Builds clean with
`sphinx-build -W`.

Co-Authored-By: Claude Opus 4.8 (1M context) <[email protected]>

8 files changed, 314 insertions, 109 deletions

diff --git a/examples/host/bare_api/README.md b/examples/host/bare_api/README.md
new file mode 100644
index 000000000..1f1341198
--- /dev/null
+++ b/examples/host/bare_api/README.md
@@ -0,0 +1,47 @@
+# Host: Bare API
+
+A USB host example that drives the TinyUSB host stack through its low-level API directly, without the higher-level class-driver application layer.
+
+## What it does
+
+- Enumerates any attached device and, on mount, fetches and prints the full device descriptor (VID/PID, USB version, class, max packet size, etc.) over the debug UART.
+- Reads and prints the manufacturer, product, and serial-number string descriptors (UTF-16 to UTF-8).
+- Fetches and walks the configuration descriptor with a small hand-written parser.
+- For any HID interface found, opens its interrupt IN endpoint with the raw endpoint API (`tuh_edpt_open` / `tuh_edpt_xfer`) and continuously prints the incoming HID reports as raw hex bytes.
+- Blinks the board LED once per second.
+
+## Requirements
+
+The board must support USB host mode (provide VBUS to the connected device); some boards need an external USB-A port / host adapter.
+
+## Configuration
+
+Notable `tusb_config.h` settings:
+
+```c
+#define CFG_TUH_ENABLED             1
+#define CFG_TUH_HUB                 1
+#define CFG_TUH_DEVICE_MAX          (3*CFG_TUH_HUB + 1)
+#define CFG_TUH_ENUMERATION_BUFSIZE 256
+#define CFG_TUH_API_EDPT_XFER       1
+```
+
+## Building
+
+CMake:
+
+```bash
+mkdir build && cd build
+cmake -DBOARD=raspberry_pi_pico ..
+cmake --build .
+```
+
+Make:
+
+```bash
+make BOARD=raspberry_pi_pico all
+```
+
+## How to use
+
+Plug any USB device (a HID keyboard/mouse works well) into the board's USB host port. On attach you should see `Device attached` followed by the full device/string/configuration descriptor dump on the debug UART. If the device exposes a HID interface, its interrupt-IN reports are printed as hex as they arrive (e.g. when you press a key or move the mouse).
diff --git a/examples/host/cdc_msc_hid/README.md b/examples/host/cdc_msc_hid/README.md
new file mode 100644
index 000000000..b59c17678
--- /dev/null
+++ b/examples/host/cdc_msc_hid/README.md
@@ -0,0 +1,59 @@
+# Host: CDC/MSC/HID
+
+A USB host example that enumerates CDC serial, Mass Storage, and HID devices and reports their activity over the debug UART.
+
+## What it does
+
+- CDC (`CFG_TUH_CDC`): bidirectionally bridges the debug console and the attached CDC serial device — bytes typed on the debug UART are written to the device, and bytes received from the device are echoed back to the UART. Also supports common USB-serial adapters (FTDI, CP210x, CH34x, PL2303). On mount it prints the interface info and line coding (set to 115200 8N1 on enumeration).
+- MSC (`CFG_TUH_MSC`): on mount, issues a SCSI Inquiry and prints the drive's vendor/product/revision strings and its capacity (block count, block size, total MB).
+- HID (`CFG_TUH_HID`): receives reports and prints keyboard keystrokes as ASCII, mouse button state and cursor movement, and any other (generic) report as raw hex.
+- Blinks the board LED once per second.
+
+## Requirements
+
+The board must support USB host mode (provide VBUS to the connected device); some boards need an external USB-A port / host adapter.
+
+## Configuration
+
+Notable `tusb_config.h` settings:
+
+```c
+#define CFG_TUH_ENABLED             1
+#define CFG_TUH_HUB                 1
+#define CFG_TUH_CDC                 1
+#define CFG_TUH_CDC_FTDI            1
+#define CFG_TUH_CDC_CP210X          1
+#define CFG_TUH_CDC_CH34X           1
+#define CFG_TUH_CDC_PL2303          1
+#define CFG_TUH_HID                 (3*CFG_TUH_DEVICE_MAX)
+#define CFG_TUH_MSC                 1
+#define CFG_TUH_DEVICE_MAX          (3*CFG_TUH_HUB + 1)
+#define CFG_TUH_HID_EPIN_BUFSIZE    64
+#define CFG_TUH_HID_EPOUT_BUFSIZE   64
+#define CFG_TUH_CDC_LINE_CONTROL_ON_ENUM  (CDC_CONTROL_LINE_STATE_DTR | CDC_CONTROL_LINE_STATE_RTS)
+#define CFG_TUH_CDC_LINE_CODING_ON_ENUM   { 115200, CDC_LINE_CODING_STOP_BITS_1, CDC_LINE_CODING_PARITY_NONE, 8 }
+```
+
+## Building
+
+CMake:
+
+```bash
+mkdir build && cd build
+cmake -DBOARD=raspberry_pi_pico ..
+cmake --build .
+```
+
+Make:
+
+```bash
+make BOARD=raspberry_pi_pico all
+```
+
+## FreeRTOS variant
+
+A FreeRTOS build is in `examples/host/cdc_msc_hid_freertos` — identical CDC/MSC/HID host behavior, running the host stack in a FreeRTOS task with a software-timer LED.
+
+## How to use
+
+Plug a USB keyboard, mouse, flash drive, or serial device into the board's USB host port (a USB hub also works, so several can be connected at once). Watch the debug UART: keystrokes and mouse movement appear as you use the input devices, an attached flash drive prints its inquiry/size info, and for a serial device you can type into the debug console to forward characters to it and see its output echoed back.
diff --git a/examples/host/device_info/README.md b/examples/host/device_info/README.md
new file mode 100644
index 000000000..79c359548
--- /dev/null
+++ b/examples/host/device_info/README.md
@@ -0,0 +1,45 @@
+# Host: Device Info
+
+A USB host example that enumerates any attached device and prints its descriptor information over the debug UART. No class drivers are enabled — only the hub driver, so it works with any kind of device.
+
+## What it does
+
+- On mount of any device, fetches and prints the full device descriptor: VID/PID, USB version, device class/subclass/protocol, max packet size, bcdDevice, and number of configurations.
+- Reads and prints the manufacturer, product, and serial-number string descriptors (UTF-16 to UTF-8), falling back to a placeholder serial when none is present.
+- Blinks the board LED, with a faster pattern while no device is mounted.
+- Builds on either the bare main loop or a FreeRTOS task, depending on `CFG_TUSB_OS`.
+
+## Requirements
+
+The board must support USB host mode (provide VBUS to the connected device); some boards need an external USB-A port / host adapter.
+
+## Configuration
+
+Notable `tusb_config.h` settings:
+
+```c
+#define CFG_TUH_ENABLED             1
+#define CFG_TUH_HUB                 1
+#define CFG_TUH_DEVICE_MAX          (3*CFG_TUH_HUB + 1)
+#define CFG_TUH_ENUMERATION_BUFSIZE 256
+```
+
+## Building
+
+CMake:
+
+```bash
+mkdir build && cd build
+cmake -DBOARD=raspberry_pi_pico ..
+cmake --build .
+```
+
+Make:
+
+```bash
+make BOARD=raspberry_pi_pico all
+```
+
+## How to use
+
+Plug any USB device into the board's USB host port. The debug UART prints the device's `ID vvvv:pppp`, serial number, and the decoded device descriptor (a hub lets you attach several devices, each printed in turn). Unplugging the device prints a removal message.
diff --git a/examples/host/hid_controller/README.md b/examples/host/hid_controller/README.md
new file mode 100644
index 000000000..861f89c5e
--- /dev/null
+++ b/examples/host/hid_controller/README.md
@@ -0,0 +1,48 @@
+# Host: HID Controller
+
+A USB host example that reads a USB game controller / gamepad (a HID device) and prints its inputs over the debug UART.
+
+## What it does
+
+- Enumerates HID devices (`CFG_TUH_HID`) and, on mount, prints the device's VID/PID.
+- Decodes reports from explicitly supported controllers — Sony DualShock 4 and a few compatible PS4 pads (Hori FC4, Hori PS4 Mini, ASW GG xrd) — printing the joystick axes (x, y, z, rz), D-pad direction, and pressed buttons (Square/Cross/Circle/Triangle, L1/R1/L2/R2, Share/Option/L3/R3, PS, touchpad click). Output is only printed when the report changes meaningfully.
+- Sends a periodic rumble output report back to the DualShock 4, with the motor intensities driven by the L2/R2 analog triggers.
+- Blinks the board LED once per second.
+
+Note: events are only shown for the explicitly supported controllers above; other HID devices enumerate but their reports are not decoded.
+
+## Requirements
+
+The board must support USB host mode (provide VBUS to the connected device); some boards need an external USB-A port / host adapter.
+
+## Configuration
+
+Notable `tusb_config.h` settings:
+
+```c
+#define CFG_TUH_ENABLED             1
+#define CFG_TUH_HUB                 0
+#define CFG_TUH_HID                 (3*CFG_TUH_DEVICE_MAX)
+#define CFG_TUH_DEVICE_MAX          (3*CFG_TUH_HUB + 1)
+#define CFG_TUH_HID_EP_BUFSIZE      64
+```
+
+## Building
+
+CMake:
+
+```bash
+mkdir build && cd build
+cmake -DBOARD=raspberry_pi_pico ..
+cmake --build .
+```
+
+Make:
+
+```bash
+make BOARD=raspberry_pi_pico all
+```
+
+## How to use
+
+Plug a supported USB game controller (e.g. a Sony DualShock 4) into the board's USB host port. Move the sticks and press buttons — the changes are printed on the debug UART, and squeezing the L2/R2 triggers makes the controller rumble.
diff --git a/examples/host/midi2_host/README.md b/examples/host/midi2_host/README.md
new file mode 100644
index 000000000..e05bc4f0a
--- /dev/null
+++ b/examples/host/midi2_host/README.md
@@ -0,0 +1,45 @@
+# Host: MIDI 2.0
+
+A minimal USB host example that receives MIDI from a connected USB-MIDI device and prints it over the debug UART, using the USB-MIDI 2.0 host driver (UMP).
+
+## What it does
+
+- Enumerates USB-MIDI devices (`CFG_TUH_MIDI2`) and, on mount, prints the negotiated protocol (MIDI 1.0 / MIDI 2.0) and the number of RX/TX cables.
+- Receives Universal MIDI Packets (UMP) and prints each one, decoding common Channel Voice messages — Note On/Off, Control Change, Program Change, Channel Pressure, Pitch Bend — for both MIDI 2.0 and MIDI 1.0 message types, and falling back to a raw hex dump for anything else.
+
+## Requirements
+
+The board must support USB host mode (provide VBUS to the connected device); some boards need an external USB-A port / host adapter.
+
+## Configuration
+
+Notable `tusb_config.h` settings:
+
+```c
+#define CFG_TUH_ENABLED             1
+#define CFG_TUH_HUB                 1
+#define CFG_TUH_DEVICE_MAX          (3*CFG_TUH_HUB + 1)
+#define CFG_TUH_MIDI2               CFG_TUH_DEVICE_MAX
+#define CFG_TUH_MIDI2_RX_BUFSIZE    512
+#define CFG_TUH_MIDI2_TX_BUFSIZE    512
+```
+
+## Building
+
+CMake:
+
+```bash
+mkdir build && cd build
+cmake -DBOARD=raspberry_pi_pico ..
+cmake --build .
+```
+
+Make:
+
+```bash
+make BOARD=raspberry_pi_pico all
+```
+
+## How to use
+
+Plug a USB-MIDI device (keyboard, controller, or interface) into the board's USB host port. On attach the debug UART prints the mount/descriptor info; then playing notes or moving controls on the device prints the decoded MIDI messages.
diff --git a/examples/host/midi_rx/README.md b/examples/host/midi_rx/README.md
new file mode 100644
index 000000000..fe29f538e
--- /dev/null
+++ b/examples/host/midi_rx/README.md
@@ -0,0 +1,44 @@
+# Host: MIDI Receive
+
+A USB host example that receives MIDI from a connected USB-MIDI device and prints the incoming bytes over the debug UART.
+
+## What it does
+
+- Enumerates USB-MIDI devices (`CFG_TUH_MIDI`) and, on mount, prints the interface index, device address, and the number of RX/TX cables.
+- On each received MIDI packet, reads the stream and prints the cable number followed by the raw MIDI bytes as hex.
+- Blinks the board LED once per second.
+
+## Requirements
+
+The board must support USB host mode (provide VBUS to the connected device); some boards need an external USB-A port / host adapter.
+
+## Configuration
+
+Notable `tusb_config.h` settings:
+
+```c
+#define CFG_TUH_ENABLED             1
+#define CFG_TUH_HUB                 1
+#define CFG_TUH_DEVICE_MAX          (3*CFG_TUH_HUB + 1)
+#define CFG_TUH_MIDI                CFG_TUH_DEVICE_MAX
+```
+
+## Building
+
+CMake:
+
+```bash
+mkdir build && cd build
+cmake -DBOARD=raspberry_pi_pico ..
+cmake --build .
+```
+
+Make:
+
+```bash
+make BOARD=raspberry_pi_pico all
+```
+
+## How to use
+
+Plug a USB-MIDI device (keyboard, controller, or interface) into the board's USB host port. On attach the debug UART prints the mount info; then playing notes or moving controls prints lines like `Cable 0 rx: 90 3C 7F` with the raw MIDI bytes.
diff --git a/examples/host/msc_file_explorer/README.md b/examples/host/msc_file_explorer/README.md
index e220bedea..b80ca8f6c 100644
--- a/examples/host/msc_file_explorer/README.md
+++ b/examples/host/msc_file_explorer/README.md
@@ -27,16 +27,38 @@ CLI is presented over the board's serial console.
 | mv      | `mv <src> <dest>`  | Rename/move a file or directory                      |
 | rm      | `rm <file>`        | Remove a file                                        |
 
+## Configuration
+
+Notable `tusb_config.h` settings:
+
+```c
+#define CFG_TUH_ENABLED       1
+#define CFG_TUH_HUB           1
+#define CFG_TUH_MSC           1
+#define CFG_TUH_DEVICE_MAX    (3*CFG_TUH_HUB + 1)
+#define CFG_TUH_MSC_MAXLUN    4
+```
+
 ## Build
 
-Build for a specific board using CMake (see [Getting Started](https://docs.tinyusb.org/en/latest/getting_started.html)):
+CMake:
+
+```bash
+mkdir build && cd build
+cmake -DBOARD=raspberry_pi_pico ..
+cmake --build .
+```
+
+Make:
 
 ```bash
-# Example: build for Raspberry Pi Pico
-cmake -B build -DBOARD=raspberry_pi_pico -DFAMILY=rp2040 examples/host/msc_file_explorer
-cmake --build build
+make BOARD=raspberry_pi_pico all
 ```
 
+## FreeRTOS variant
+
+A FreeRTOS build is in `examples/host/msc_file_explorer_freertos` — identical MSC FatFS file-explorer CLI, running the host stack and CLI as FreeRTOS tasks.
+
 ## Usage
 
 1. Flash the firmware to your board.
diff --git a/examples/host/msc_file_explorer_freertos/README.md b/examples/host/msc_file_explorer_freertos/README.md
deleted file mode 100644
index 4ee6b96fa..000000000
--- a/examples/host/msc_file_explorer_freertos/README.md
+++ /dev/null
@@ -1,105 +0,0 @@
-# MSC File Explorer (FreeRTOS)
-
-This host example implements an interactive command-line file browser for USB Mass Storage devices.
-When a USB flash drive is connected, the device is automatically mounted using FatFS and a shell-like
-CLI is presented over the board's serial console.
-
-## Features
-
-- Automatic mount/unmount of USB storage devices
-- FAT12/16/32 filesystem support via FatFS
-- Interactive CLI with command history
-- Read speed benchmarking with `dd`
-- Support for up to 4 simultaneous USB storage devices (via hub)
-
-## Supported Commands
-
-| Command | Usage              | Description                                          |
-|---------|--------------------|------------------------------------------------------|
-| help    | `help`             | Print list of available commands                     |
-| cat     | `cat <file>`       | Print file contents to the console                   |
-| cd      | `cd <dir>`         | Change current working directory                     |
-| cp      | `cp <src> <dest>`  | Copy a file                                          |
-| dd      | `dd [count]`       | Read sectors and report speed (default 1024 sectors) |
-| ls      | `ls [dir]`         | List directory contents                              |
-| pwd     | `pwd`              | Print current working directory                      |
-| mkdir   | `mkdir <dir>`      | Create a directory                                   |
-| mv      | `mv <src> <dest>`  | Rename/move a file or directory                      |
-| rm      | `rm <file>`        | Remove a file                                        |
-
-## Build
-
-Build for a specific board using CMake (see [Getting Started](https://docs.tinyusb.org/en/latest/getting_started.html)):
-
-```bash
-# Example: build for STM32F407 Discovery board
-cmake -B build -DBOARD=stm32f407disco -GNinja examples/host/msc_file_explorer_freertos
-cmake --build build
-```
-
-## Usage
-
-1. Flash the firmware to your board.
-2. Open a serial terminal (e.g. `minicom`, `screen`, `PuTTY`) at 115200 baud.
-3. Plug a USB flash drive into the board's USB host port.
-4. The device is auto-mounted and the prompt appears:
-
-```
-TinyUSB MSC File Explorer Example
-
-Device connected
-  Vendor  : Kingston
-  Product : DataTraveler 2.0
-  Rev     : 1.0
-  Capacity: 1.9 GB
-
-0:/> _
-```
-
-### Browsing Files
-
-```
-0:/> ls
-----a    1234  readme.txt
-d----       0  photos
-d----       0  docs
-
-0:/> cd photos
-0:/photos> ls
-----a  520432  vacation.jpg
-----a  312088  family.png
-
-0:/> cat readme.txt
-Hello from USB drive!
-```
-
-### Copying and Moving Files
-
-```
-0:/> cp readme.txt backup.txt
-0:/> mv backup.txt docs/backup.txt
-```
-
-### Measuring Read Speed
-
-```
-0:/> dd
-Reading 1024 sectors...
-  Data speed: 823 KB/s
-```
-
-### Multiple Devices
-
-When using a USB hub, multiple drives are mounted as `0:`, `1:`, etc. Use the drive prefix to
-navigate between them:
-
-```
-0:/> cd 1:
-1:/> ls
-```
-
-## Testing
-
-Build-time validation follows the standard TinyUSB host example flow. Runtime behavior should be
-verified on hardware by attaching an MSC device and exercising CLI commands such as `ls`, `pwd`,
-and `dd`.