Music daemon + cross-source sync via OBS WebSocket

Music persistence across scene switches by extracting playback into a
separate browser source (music/index.html) — single source instance
shared across scenes via OBS's "Add Existing", so it doesn't restart on
scene change.

Loading and Game overlays subscribe to mpd:state CustomEvents over OBS
WebSocket; the daemon broadcasts at 1 Hz plus on every track change.
File-based command pipeline lets bash control playback without a
WebSocket client of its own:

- vendor/obs-ws-mini.js — minimal WS v5 client with HMAC-SHA256 auth,
  hard timeout, close-rejection, and a pure-JS SHA-256 fallback for
  CEF file:// origins where crypto.subtle is unavailable.
- setup.sh — generates vendor/obs-config.js from the OBS plugin config;
  checks the live socket instead of the (lagging) config file.
- music/index.html — invisible audio worker. Plays through a shuffled
  queue with hardened error/stall recovery, polls loading/cmd.js for
  bash-issued commands, broadcasts mpd:state via WS. Includes a
  diagnostic status block (visible if the source's eye-icon is on).
- loading/index.html — strips local audio playback; subscribes to
  mpd:state to drive the now-playing terminal line live. Removes the
  redundant trailing prompt; terminal lines anchor at the bottom.
- loading/playlist.sh — rebuilt as subcommand API:
    sync (default), skip, prev, pause, resume, status
  control commands write loading/cmd.js (id, type, ts), which the
  daemon polls every 250ms.
- loading/convert.sh — strips video tracks from .webm music downloads
  to audio-only m4a (~95% smaller, ~20× faster decode); fixes the
  CPU pegging from CEF decoding 1080p VP9 video for music playback.
- .gitignore — track manifests, ignore generated wrappers + secrets +
  the audio cache.

setup.sh

@@ -0,0 +1,56 @@
+#!/usr/bin/env bash
+# One-time setup: builds vendor/obs-config.js from your existing OBS WebSocket
+# plugin config so the overlay/daemon pages can connect.
+#
+#   ./setup.sh
+#
+# Re-run if you change the WebSocket port or password in OBS.
+set -euo pipefail
+
+DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
+SRC="$DIR/plugin_config/obs-websocket/config.json"
+OUT="$DIR/vendor/obs-config.js"
+
+if [[ ! -f "$SRC" ]]; then
+  echo "  ✗ $SRC not found." >&2
+  echo "    Open OBS once with the obs-websocket plugin loaded so it generates the config." >&2
+  exit 1
+fi
+
+# Pull port + password out of the JSON
+read -r PORT PASS ENABLED <<<"$(python3 -c "
+import json, sys
+d = json.load(open('$SRC'))
+print(d.get('server_port', 4455), d.get('server_password', ''), str(d.get('server_enabled', False)).lower())
+")"
+
+mkdir -p "$DIR/vendor"
+cat > "$OUT" <<JS
+// Auto-generated by setup.sh — gitignored. Reflects the current contents of
+// plugin_config/obs-websocket/config.json. Re-run setup.sh if it changes.
+window.__OBSWS = {
+  url:      'ws://localhost:$PORT',
+  password: '$PASS',
+};
+JS
+
+echo "  ✓ wrote $OUT"
+echo "    url      = ws://localhost:$PORT"
+if [[ -z "$PASS" ]]; then
+  echo "    password = (none)"
+else
+  echo "    password = (set, ${#PASS} chars)"
+fi
+
+# Check the live socket, not the config file — OBS lags writes to plugin_config
+# until shutdown, so server_enabled in JSON often disagrees with reality.
+echo
+if ss -lnt 2>/dev/null | grep -q ":$PORT "; then
+  echo "  ✓ OBS WebSocket server is listening on :$PORT"
+elif nc -z localhost "$PORT" 2>/dev/null; then
+  echo "  ✓ OBS WebSocket server is listening on :$PORT"
+else
+  echo "  ⚠ Nothing listening on :$PORT yet."
+  echo "    In OBS:  Tools → WebSocket Server Settings → ✅ Enable WebSocket server → OK"
+  echo "    (config.json may already say 'enabled: $ENABLED' — that file lags actual state)"
+fi