feat(hub): Music app client — album grid, flat list, persistent player

Implements the client half of docs/musicbay.md against MNP 0.8:

- music-app.js: album grid (grouped by artist -> album, from index-time
  artist/album fields) or flat folder view, per-group localStorage
  toggle like Videos. MusicBrainz (music_meta_req) is only looked up
  when a track has no embedded cover at all — well-tagged files never
  trigger a network call, unlike Videos where TMDB is unconditional.
  Reuses video-app.js's MediaThumb/LazyTile (now exported) rather than
  duplicating the chunk-path thumbnail decode + virtualization.
- music-player.js: the persistent player bar — queue, shuffle (Fisher-
  Yates, keeps the current track in place when toggled), repeat (off/
  all/one), volume (localStorage), prev/next, a one-track prefetch
  cache. No MSE, no node-side streaming: a track is downloaded and
  decrypted once via file-utils.js's pipelinedDownload, same chunk
  pipeline Files already uses, then played from a blob URL.
- group-page.js: owns musicQueue/musicbrainzConfig state and renders
  MusicPlayerBar outside the tab-switched area — deliberately, so
  playback survives navigating to Chat/Files, the same reasoning the
  video/preview modals are shell-owned rather than app-owned.
- apps.js: registers "music". transport.js: fetchMusicMeta (keyed by
  path, same reordering-hazard fix as fetchMediaMeta),
  setMusicbrainzConfig/setMusicbrainzEnabled (signed ops, mirroring
  TMDB's), and the three new ack handlers. group-settings.js: a
  MusicBrainz settings section (contact string, per-group toggle) —
  the existing Applications checklist already picks up "music" for
  free, per apps.md's own claim.
- icon.js: music/pause/skip-next/skip-prev/shuffle/repeat/volume,
  drawn in the same stroked style as the existing set.
- i18n: group.tab_music, the music.* and settings_node.musicbrainz_*
  keys, translated (not just copied) across all ten locales, Polish
  carrying full one/few/many/other plural forms for music.n_tracks.
- webapp.py's _ASSETS, test_hook_ordering.py's STATIC_FILES and
  test_transport_contracts.py's SPLIT_FILES gain the two new files.

Full suite (common + hub + node): 1116 passed, no regressions.
`npm run sync-ui` in meshbay-client confirmed both files copied.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01KBi7ALLGfwcjBXt57yNMcy

1 files changed, 250 insertions, 0 deletions

diff --git a/packages/meshbay-hub/src/meshbay_hub/static/style.css b/packages/meshbay-hub/src/meshbay_hub/static/style.css
index 446a751..b4e4089 100644
--- a/packages/meshbay-hub/src/meshbay_hub/static/style.css
+++ b/packages/meshbay-hub/src/meshbay_hub/static/style.css
@@ -2685,3 +2685,253 @@ a.transfer-name {
   object-fit: cover;
   border-radius: 4px;
 }
+
+/* ── Music app (docs/musicbay.md) ─────────────────────────────────────────
+   Reuses .video-overlay/.video-top-bar/.video-title/.video-close, .tb-btn/
+   .tb-search, .video-flat-list/.video-flat-row/.video-flat-info/
+   .video-flat-title/.video-flat-sub/.video-flat-folder/.video-flat-chevron
+   and .video-thumb-empty as-is — only what's genuinely different from
+   Videos (album art is square, not 2:3; there is a persistent player bar;
+   grouping is artist -> album, not movie/show) gets its own rule below. */
+
+.music-artist-section { margin-bottom: 22px; }
+.music-artist-heading {
+  font-size: 0.95em;
+  font-weight: 600;
+  margin: 0 0 10px;
+  color: var(--text);
+}
+
+.music-grid {
+  display: grid;
+  grid-template-columns: repeat(auto-fill, minmax(150px, 1fr));
+  gap: 16px;
+}
+.music-tile-slot { min-height: 200px; }
+
+.music-card {
+  cursor: pointer;
+  border-radius: 8px;
+  overflow: hidden;
+  background: var(--bg-raised);
+  border: 1px solid var(--border);
+  transition: border-color 0.12s, transform 0.12s;
+}
+.music-card:hover { border-color: var(--accent); transform: translateY(-2px); }
+
+.music-cover {
+  width: 100%;
+  aspect-ratio: 1 / 1;
+  object-fit: cover;
+  display: block;
+  background: var(--bg-surface);
+}
+.music-cover.video-thumb-empty { aspect-ratio: 1 / 1; }
+
+.music-card-info { padding: 8px 10px; }
+.music-card-title {
+  font-size: 0.88em;
+  font-weight: 600;
+  overflow: hidden;
+  text-overflow: ellipsis;
+  white-space: nowrap;
+}
+.music-card-sub {
+  font-size: 0.78em;
+  color: var(--text-dim);
+  margin-top: 2px;
+  overflow: hidden;
+  text-overflow: ellipsis;
+  white-space: nowrap;
+}
+
+/* Detail modal — sits inside the shared .video-overlay */
+
+.music-detail {
+  width: min(560px, 92vw);
+  max-height: calc(100vh - 100px);
+  margin-top: 60px;
+  background: var(--bg-surface);
+  border-radius: 10px;
+  overflow: hidden;
+  display: flex;
+  flex-direction: column;
+}
+.music-detail .video-top-bar {
+  position: static;
+  background: var(--bg-raised);
+  border-bottom: 1px solid var(--border);
+}
+.music-detail .video-title { color: var(--text); }
+.music-detail .video-close { background: var(--bg-surface); color: var(--text); }
+.music-detail .video-close:hover { background: var(--border); }
+
+.music-detail-body { padding: 16px 20px; overflow-y: auto; }
+.music-detail-header {
+  display: flex;
+  align-items: flex-start;
+  gap: 14px;
+  margin-bottom: 14px;
+}
+.music-detail-cover {
+  width: 96px;
+  height: 96px;
+  aspect-ratio: 1 / 1;
+  object-fit: cover;
+  border-radius: 6px;
+  flex-shrink: 0;
+  background: var(--bg-raised);
+}
+.music-detail-meta { min-width: 0; }
+.music-detail-artist { font-weight: 600; font-size: 0.95em; }
+.music-detail-date { font-size: 0.8em; color: var(--text-dim); margin: 2px 0 8px; }
+
+.music-tracklist { display: flex; flex-direction: column; gap: 2px; }
+.music-track-row {
+  display: flex;
+  align-items: center;
+  gap: 10px;
+  width: 100%;
+  padding: 6px 8px;
+  background: none;
+  border: 1px solid transparent;
+  border-radius: 6px;
+  color: var(--text);
+  font-size: 0.85em;
+  cursor: pointer;
+  text-align: left;
+}
+.music-track-row:hover { background: var(--bg-raised); border-color: var(--border); }
+.music-track-no { width: 24px; flex-shrink: 0; color: var(--text-dim); text-align: right; }
+.music-track-title { flex: 1; min-width: 0; overflow: hidden; text-overflow: ellipsis; white-space: nowrap; }
+.music-track-duration { color: var(--text-dim); font-size: 0.9em; flex-shrink: 0; }
+
+/* Mode B — flat list. .video-flat-thumb-slot's sizing is reused verbatim;
+   only the empty-box icon differs, so it gets a name of its own. */
+.music-flat-thumb {
+  width: 64px;
+  height: 40px;
+  flex-shrink: 0;
+  border-radius: 4px;
+  border: 1px solid var(--border);
+}
+
+/* ── Persistent player bar (docs/musicbay.md §2.3) ────────────────────────
+   `position: sticky`, not `fixed` — deliberately: CLAUDE.md's own history
+   records more than one layout bug from a fixed-position element quietly
+   double-reserving space against a page that also sized itself against the
+   viewport. Sticky stays in normal flow, so it never needs a height this
+   stylesheet has to know about anywhere else. */
+.music-player-bar {
+  position: sticky;
+  bottom: 0;
+  z-index: 50;
+  display: flex;
+  align-items: center;
+  gap: 16px;
+  flex-wrap: wrap;
+  margin-top: 16px;
+  padding: 8px 16px;
+  background: var(--bg-raised);
+  border: 1px solid var(--border);
+  border-radius: 10px;
+}
+
+.music-player-info {
+  display: flex;
+  align-items: center;
+  gap: 10px;
+  min-width: 0;
+  flex: 1 1 160px;
+}
+.music-player-icon { width: 20px; height: 20px; color: var(--text-dim); flex-shrink: 0; }
+.music-player-text { min-width: 0; }
+.music-player-title {
+  font-size: 0.85em;
+  font-weight: 600;
+  overflow: hidden;
+  text-overflow: ellipsis;
+  white-space: nowrap;
+}
+.music-player-sub {
+  font-size: 0.75em;
+  color: var(--text-dim);
+  overflow: hidden;
+  text-overflow: ellipsis;
+  white-space: nowrap;
+}
+
+.music-player-transport {
+  display: flex;
+  align-items: center;
+  gap: 4px;
+  flex-shrink: 0;
+}
+.music-player-btn {
+  background: none;
+  border: none;
+  color: var(--text-dim);
+  width: 32px;
+  height: 32px;
+  border-radius: 50%;
+  display: flex;
+  align-items: center;
+  justify-content: center;
+  cursor: pointer;
+  position: relative;
+}
+.music-player-btn:hover { background: var(--bg-surface); color: var(--text); }
+.music-player-btn.active { color: var(--accent); }
+.music-player-btn .icon { width: 16px; height: 16px; }
+.music-player-play {
+  width: 38px;
+  height: 38px;
+  background: var(--accent);
+  color: var(--accent-text);
+}
+.music-player-play:hover { background: var(--accent-hover); color: var(--accent-text); }
+.music-player-play:disabled { opacity: 0.6; cursor: not-allowed; }
+.music-repeat-badge {
+  position: absolute;
+  bottom: 1px;
+  right: 1px;
+  font-size: 0.55em;
+  font-weight: 700;
+  line-height: 1;
+  background: var(--accent);
+  color: var(--accent-text);
+  border-radius: 50%;
+  width: 11px;
+  height: 11px;
+  display: flex;
+  align-items: center;
+  justify-content: center;
+}
+
+.music-player-seek {
+  display: flex;
+  align-items: center;
+  gap: 8px;
+  flex: 2 1 200px;
+  min-width: 120px;
+}
+.music-player-time { font-size: 0.75em; color: var(--text-dim); flex-shrink: 0; width: 34px; }
+.music-player-time:last-child { text-align: right; }
+.music-player-seek input[type="range"] { flex: 1; }
+
+.music-player-volume {
+  display: flex;
+  align-items: center;
+  gap: 6px;
+  flex-shrink: 0;
+}
+.music-player-volume .icon { width: 16px; height: 16px; color: var(--text-dim); }
+.music-player-volume input[type="range"] { width: 80px; }
+
+.music-player-error { flex-basis: 100%; font-size: 0.78em; color: var(--error); }
+
+@media (max-width: 640px) {
+  .music-player-bar { gap: 8px; }
+  .music-player-seek { order: 4; flex-basis: 100%; }
+  .music-player-volume { display: none; }
+}