Feat/library stems midi first class

[danieljtrujillo]

[feat(questcast): stream Quest headset video into the VJ as a live source]

Adds a scrcpy-protocol relay sidecar (sidecars/questcast, @yume-chan ADB +
AdbScrcpyOptions3_3_3) that pipes raw H.264 over a WebSocket, plus the
backend questcast module that supervises it and exposes status/devices with
a verbose log ring buffer for field debugging.

The browser side decodes via WebCodecs into an offscreen canvas and
captureStream()s it as a VJ camera source. The key fix for the
"keyframes decode but nothing renders" symptom: scrcpy sends SPS/PPS in a
separate config packet, so those bytes are prepended to every keyframe
chunk before feeding the decoder.

VJView drops the floating double-decode preview (the right-panel preview
reuses the single stream) and gains clipboard-write on the iframe allow so
the in-VJ log copy button works.

core/adb.py centralises adb path resolution shared by questcast/questmidi.

[feat(broadcast): WebRTC watch-link signaling for the live VJ output]

Phase 1 backend of the watch-link feature: a tiny signaling relay so viewers
can watch the live VJ output (with audio) over a shareable link. Media stays
peer-to-peer — only SDP/ICE pass through the relay — so the venue LAN gets
full quality and low latency.

GET /api/broadcast/link room id + LAN/public watch URLs + ICE config
GET /api/broadcast/watch/{room} self-contained WebRTC viewer page
WS /api/broadcast/ws rooms, routes offer/answer/ice by viewer id

STUN always; optional TURN from theDAW_TURN_URL/USER/PASS env for public
reach. Public base from theDAW_PUBLIC_BASE. The VJ-side GO LIVE broadcaster
(captureStream of the output canvas + audio) is the next phase.

[feat(vj): native OS folder picker for VJ export output]

Replaces the typed export path with a real OS folder dialog. core/folder_dialog
opens a Windows FolderBrowserDialog (PowerShell, -STA, topmost) with a tkinter
fallback. The vj module gains GET /export-folder and POST /export-folder/pick,
the latter persisting the chosen vj.export_root via the settings patch.

[fix(backend): repair MIDI/basic-pitch deps and Quest adb resolution]

Three field-incident fixes:

• Pin setuptools<81 so basic-pitch's legacy pkg_resources import keeps
  working; setuptools >= 81 removed it and broke MIDI conversion with
  "No module named 'pkg_resources'".
• midi/engine.py re-exposes librosa.core.audio.{to_mono,resample,util} as a
  compat shim for piano_transcription_inference, which librosa 0.11 moved.
• questmidi/bridge.py resolves adb through the shared core.adb helper.

[chore: ignore node_modules globally; record VJ work + queued punchlist]

.gitignore now ignores node_modules/ everywhere (frontend + sidecars) so
package trees never get vendored. Appends section 9 to the global-layout plan
capturing what landed (Quest streaming, layout, cymatics, dep fixes, broadcast
phase 1) and the queued VJ UI punchlist