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]>

1 files changed, 11 insertions, 0 deletions

diff --git a/examples/dual/dynamic_switch/README.md b/examples/dual/dynamic_switch/README.md
index 034787f18..94b161480 100644
--- a/examples/dual/dynamic_switch/README.md
+++ b/examples/dual/dynamic_switch/README.md
@@ -9,6 +9,17 @@ This example demonstrates TinyUSB's dual-role capability by allowing runtime swi
 - **Host Mode**: Enumerates connected USB devices and prints device information
 - **Dynamic switching**: Deinitializes the current stack and reinitializes in the new mode
 
+## Configuration
+
+Notable `tusb_config.h` settings:
+
+```c
+#define CFG_TUD_CDC 1
+#define CFG_TUH_HUB 1
+#define CFG_TUH_DEVICE_MAX (CFG_TUH_HUB ? 4 : 1)
+#define CFG_TUH_ENUMERATION_BUFSIZE 256
+```
+
 ## Usage
 
 1. **Build and flash** the example to your board