feat: add realtime robot conversation tools - #579

Summary

• Add built-in robot tools for Realtime Conversation: set_emotion, play_motion, optional set_led, play_melody, and get_robot_status.
• Reuse a single modern AudioOut through a four-track software mixer so conversation audio and melody/tone playback can coexist.
• Suspend only microphone input during melody playback while preserving the Realtime connection and output path.

What Changed

• Add recursive tool parameter schemas and safe argument validation.
• Expose the latest successful IMU sample for robot status.
• Migrate Speaker to the modern streaming AudioOut API and route supported platforms through the shared mixer.
• Integrate the shared robot tools into the chat_audioio MOD.
• Add unit, Moddable, and architecture coverage.
• Release impact: minor
• Changeset: .changeset/realtime-robot-tools.md

Verification

• cd firmware && npm run format
• cd firmware && npm run lint
• cd firmware && npx biome ci . --error-on-warnings
• cd firmware && npm run test:unit (48/48)
• cd firmware && npm run test:moddable (33/33 manifests)
• cd firmware && npm run check:architecture
• cd firmware && npm run check:legacy-names
• cd firmware && npm run check:manifest
• cd firmware && npm run build:m5stackchan_cores3
• cd firmware && npm run build:stackchan_rt
• cd firmware && npm run mod:m5stackchan_cores3 -- mods/examples/chat_audioio/manifest.json -t build
• cd firmware && npm run mod:stackchan_rt -- mods/examples/chat_audioio/manifest.json -t build
• Hardware test (deferred because the connected device is currently in use by another task)

Affected Areas

• firmware
• web
• schematics
• case
• docs
• ci/github-actions

Breaking Changes

• none
• yes, described below

Related Issues

• None