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, 0 insertions, 19 deletions

diff --git a/examples/device/audio_test_freertos/README.md b/examples/device/audio_test_freertos/README.md
deleted file mode 100644
index 9477fcd78..000000000
--- a/examples/device/audio_test_freertos/README.md
+++ /dev/null
@@ -1,19 +0,0 @@
-# How to build example for Esp32s3
-1. Load idf environment variables (eg. using the esp-idf alias `get_idf` if configured)
-
-2. cd into examples directory
-```
-$ cd /tinyusb/examples/device/audio_test_freertos
-```
-
-3. Run cmake in project directory specifying the board
-```
-$ cmake -DBOARD=espressif_s3_devkitc -B build -G Ninja .
-$ ninja.exe -C build
-```
-
-4. Flash the binary onto the esp32-s3 by copy-paste of the full command output by the esp-idf build system replacing **(PORT)** with eg. /dev/ttyUSB0
-
-eg.
-
-> /home/kaspernyhus/.espressif/python_env/idf4.4_py3.8_env/bin/python ../../../../esp-idf/components/esptool_py/esptool/esptool.py -p /dev/ttyUSB0 -b 460800 --before default_reset --after hard_reset --chip esp32s3  write_flash --flash_mode dio --flash_size detect --flash_freq 80m 0x0 _build/espressif_s3_devkitc/bootloader/bootloader.bin 0x8000 _build/espressif_s3_devkitc/partition_table/partition-table.bin 0x10000 _build/espressif_s3_devkitc/audio_test_freertos.bin