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.

loading/loading.sh

@@ -0,0 +1,119 @@
+#!/usr/bin/env bash
+# Interactive manifest builder for the Project Loading scene.
+#
+#   ./loading.sh
+#
+# Walks you through 5 prompts, writes loading.json + loading.js, then
+# refresh the Project Loading browser source in OBS.  Re-running uses
+# previous answers as defaults — press Enter to keep them.
+set -euo pipefail
+
+DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
+JSON="$DIR/loading.json"
+JS="$DIR/loading.js"
+
+# Reads a top-level field from the previous loading.json. Always exits 0;
+# prints empty string if file/field is missing.
+prev() {
+  [[ -f "$JSON" ]] || return 0
+  python3 - "$JSON" "$1" <<'PY' 2>/dev/null || true
+import json, sys
+try:
+    d = json.load(open(sys.argv[1]))
+    v = d.get(sys.argv[2])
+    if v is None:                print('')
+    elif isinstance(v, bool):    print('y' if v else 'n')
+    else:                        print(v)
+except Exception:
+    pass
+PY
+}
+
+ask() {
+  # ask "question" "default" → echoes user input or default if blank
+  local q="$1" def="${2:-}"
+  local prompt="  $q"
+  [[ -n "$def" ]] && prompt+="  [$def]"
+  prompt+=": "
+  local v
+  read -rp "$prompt" v
+  [[ -z "$v" && -n "$def" ]] && v="$def"
+  printf '%s' "$v"
+}
+
+ask_yn() {
+  local v; v=$(ask "$1" "${2:-y}")
+  case "${v,,}" in
+    y|yes|on|true|1)  printf 'true'  ;;
+    n|no|off|false|0) printf 'false' ;;
+    *)                printf 'true'  ;;
+  esac
+}
+
+ask_int() {
+  local v
+  while :; do
+    v=$(ask "$1" "${2:-}")
+    [[ "$v" =~ ^[0-9]+$ ]] && { printf '%s' "$v"; return; }
+    echo "  ✗ must be a whole number" >&2
+  done
+}
+
+sanitize() {
+  printf '%s' "${1:-}" \
+    | tr -d '"\\' \
+    | tr '\n\r\t' '   ' \
+    | sed 's/  */ /g; s/^ //; s/ $//'
+}
+emit_str() { [[ -z "${1:-}" ]] && printf 'null' || printf '"%s"' "$1"; }
+
+# ── Pull previous answers as defaults ───────────────
+prev_game=$(prev game)
+prev_subtitle=$(prev subtitle)
+prev_count=$(prev countdownMin); [[ -z "$prev_count"  ]] && prev_count="5"
+prev_camera=$(prev camera);      [[ -z "$prev_camera" ]] && prev_camera="y"
+prev_mic=$(prev microphone);     [[ -z "$prev_mic"    ]] && prev_mic="y"
+
+echo "── Project Loading manifest ──"
+echo "  (press Enter to keep [defaults])"
+echo
+
+game=$(ask "Game" "$prev_game")
+while [[ -z "$game" ]]; do
+  echo "  ✗ Game is required" >&2
+  game=$(ask "Game" "")
+done
+
+subtitle=$(ask    "Subtitle (mode / episode / note)" "$prev_subtitle")
+countdown=$(ask_int "Countdown (minutes)"            "$prev_count")
+camera=$(ask_yn   "Camera"                           "$prev_camera")
+mic=$(ask_yn      "Microphone"                       "$prev_mic")
+
+game=$(sanitize "$game")
+subtitle=$(sanitize "$subtitle")
+
+now_iso=$(date -u +%FT%TZ)
+tmp="$JSON.tmp.$$"
+cat > "$tmp" <<JSON
+{
+  "compiledAt":   "$now_iso",
+  "game":         $(emit_str "$game"),
+  "subtitle":     $(emit_str "$subtitle"),
+  "countdownMin": $countdown,
+  "camera":       $camera,
+  "microphone":   $mic
+}
+JSON
+
+if ! python3 -m json.tool "$tmp" >/dev/null 2>&1; then
+  echo "  ✗ produced invalid JSON, leaving $tmp for inspection" >&2
+  exit 1
+fi
+mv -f "$tmp" "$JSON"
+{ printf 'window.__LOADING = '; cat "$JSON"; printf ';\n'; } > "$JS.tmp.$$"
+mv -f "$JS.tmp.$$" "$JS"
+
+echo
+echo "  ✓ wrote $JSON"
+echo "  ✓ wrote $JS"
+echo "  → refresh the Project Loading browser source in OBS."