library: MusicBrainz text matching + Match-Review UI (P8) (#710)

* library: MusicBrainz text matching + Match-Review UI — P8

Replaces the enrichment plumbing's no-op matcher (P7) with the real
pipeline, per the library-metadata design: a wrong match is worse than a
slow one, so medium confidence goes to a human review queue and never
straight to canonical values.

- lib/mb_match.py (new, pure — no network/DB/server imports): denoise
  (author credits, (440Hz)/(Live)/(No Lead)/(v2) parentheticals,
  diacritics/punctuation, ACDC / AC DC / AC/DC folding via compacted
  token equality), token-set similarity, scoring with year/duration
  corroboration bonuses, tier classification (auto needs combined
  >= 0.95 AND per-field floors — a perfect-title cover by the wrong
  artist, or a chart with no artist, can never auto-match), Lucene
  query building, MusicBrainz response normalization.
- Matcher precedence in _enrich_one: content-hash cache copy (another
  chart of the same recording matches with no network) -> manifest
  mbid (tier 0) / isrc (tier 1) exact keys, feature-detected and
  strictly shape-validated, read-only -> text search tiers
  (auto / review / failed).
- Lifecycle: review rows store their ranked candidate list (JSON) and
  write NO canonical fields until a human accepts; failed rows retry on
  an exponential backoff (1 h doubling, 7 d cap) via the attempts
  column; user-rejected rows never auto-retry; an identity edit
  re-queues anything and resets the backoff; never-overwrite-manual is
  enforced inside the single writer (apply_enrichment_match) so no call
  path can forget it.
- Network: _mb_http_get is the one transport seam — throttled to
  <= 1 req/s through P7's _enrich_throttle, identified with a real
  User-Agent from VERSION, and a 503 pauses the whole pass without
  burning attempts. Offline guard: no sockets under
  FEEDBACK_ENRICH_OFFLINE or FEEDBACK_SKIP_STARTUP_TASKS, so pytest can
  never reach MusicBrainz; the pass still stamps identity hashes
  (two-phase), which is why every P7 test passes unchanged.
- Routes: GET /api/enrichment/review, POST
  /api/enrichment/review/{filename}/accept|reject|pick, GET
  /api/enrichment/search (throttled manual-search proxy). All four are
  demo-mode blocked.
- Match facet: match= CSV accepted by /api/library AND
  /api/library/stats (the A-Z rail's letter counts stay lockstep with
  the grid) — review / matched (incl. manual) / unmatched / pending,
  the same EXISTS idiom as the mastery facet.
- UI: static/v3/match-review.js (new, self-contained) — an ambient
  "N to review" chip beside the song count (rendered only when
  non-zero; silent on success, no toasts), and a review drawer on the
  filter-drawer slide idiom (Escape + focus trap; row click accepts,
  "Not a match" rejects, "Search instead" is the fix-match escape
  hatch). songs.js gets the chip mount, a Match filter section, and
  session-only match state; also fixes the latent applySavedPrefs bug
  where restored filters dropped the mastery key, which made the
  filter drawer throw for anyone with saved prefs.
- static/tailwind.min.css regenerated (scripts/build-tailwind.sh) for
  the new utility classes; conflicts with sibling PRs resolve by
  re-running the script.

Nothing is ever written to pack files — canonical values live only in
the song_enrichment display cache. Cover art caching and acoustic
fingerprinting are follow-up slices.

22 pure unit tests + 19 server tests (fake transport injected over the
_mb_http_get seam) + demo-mode route cases; full-suite failure set
A/B-identical with the change stashed vs applied.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Nm7tHs1Yvjjtnnu4nzJgdN

* library: match-review modal + configurable auto-apply confidence (P8 R0)

Follow-up to the initial P8 commit, folding in the first round of tester
feedback on the review surface and the matcher's knobs:

- Review GUI is a centred MODAL now, not a sidebar — one chart at a
  time (the scraper-review model from media-server / emulation-frontend
  apps): the chart's current metadata with explicit amber
  "Missing: album / year / cover art" chips (art detected via the art
  request failing), candidates each carrying "Adds: year - genres -
  ISRC" / "Shows as: ACDC -> AC/DC" per-field chips, and Skip /
  Not a match / Search instead / Use selected with prev-next + arrow-key
  navigation. Chip + window API surface unchanged, so songs.js needed no
  edits for the rework.
- Auto-apply confidence is a SETTING: default drops 0.95 -> 0.90
  (mb_match.AUTO_MIN; classify() takes an auto_min override). The
  per-field floors are untouched and threshold-independent — a
  perfect-title cover by the wrong artist still can't auto-match at any
  setting. New validated settings keys: enrich_enabled (bool) +
  enrich_auto_threshold (0.5–1.01; >1.0 = "Always review", since a
  capped score can equal exactly 1.0). Read once per pass; disabling
  gates only the BACKGROUND matcher — manual search/fix stays available.
- Settings -> Library -> "Metadata matching" card: enable toggle,
  confidence select (85 / 90 / 95 / Always review), a Match Now button
  (new POST /api/enrichment/kick, single-flight like every other kick,
  demo-mode blocked), and a live status line fed by the same fetch as
  the review chip. Markup in index.html per the v3 settings pattern,
  wired by match-review.js, null-guarded so v2 no-ops.
- Review queue orders missing-data charts first — confirming those has
  the most to gain; complete charts only stand to be re-labelled.

Tests: threshold moves the auto/review boundary via settings; the
enable toggle gates matching but not the manual proxy; settings
validation; kick route; queue ordering; classify(auto_min=...) floors.
Full-suite failure set byte-identical to the pre-change baseline.
tailwind.min.css regenerated for the modal's utility classes.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Nm7tHs1Yvjjtnnu4nzJgdN

* fix(library): lock MusicBrainz throttle across sleep + de-dup enrich queue (PR #710 review)

Hold a module-level lock across _enrich_throttle's read/sleep/write so the
background daemon and threadpooled sync search route serialize outbound MB
requests instead of bursting past the 1 req/s limit. De-dup the enrich queue
by filename so a changed-hash failed row isn't processed twice per pass.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

---------

Co-authored-by: Claude Fable 5 <noreply@anthropic.com>
Co-authored-by: byrongamatos <xasiklas@gmail.com>

static/v3/songs.js

@@ -59,7 +59,7 @@
         artist: '', album: '',
         grouping: true,     // one card per song (multi-chart grouping); persisted
 
-        filters: { arr_has: [], arr_lacks: [], stem_has: [], stem_lacks: [], lyrics: '', tunings: [], mastery: [] },
+        filters: { arr_has: [], arr_lacks: [], stem_has: [], stem_lacks: [], lyrics: '', tunings: [], mastery: [], match: [] },
         page: 0, total: 0, loading: false, built: false, accuracy: {}, tuningNames: [],
         artistCatalog: [], renderedHash: '',
         scrollBound: false,
@@ -110,6 +110,7 @@
         const f = state.filters;
         return f.arr_has.length + f.arr_lacks.length + f.stem_has.length + f.stem_lacks.length +
             (f.lyrics ? 1 : 0) + f.tunings.length + (f.mastery ? f.mastery.length : 0) +
+            (f.match ? f.match.length : 0) +
             (state.artist ? 1 : 0) + (state.album ? 1 : 0);
     }
 
@@ -133,6 +134,7 @@
                 lyrics: f.lyrics || '',
                 tunings: [...(f.tunings || [])].sort(),
                 mastery: [...(f.mastery || [])].sort(),
+                match: [...(f.match || [])].sort(),
             },
         });
     }
@@ -155,10 +157,15 @@
         const f = saved.filters;
         if (f && typeof f === 'object') {
             const arr = (x) => (Array.isArray(x) ? x.slice() : []);
+            // mastery + match are session-only facets (deliberately not
+            // persisted), but the restored object must still CARRY the keys —
+            // the filter drawer indexes f.mastery/f.match unconditionally, so
+            // dropping them here breaks the drawer for anyone with saved prefs.
             state.filters = {
                 arr_has: arr(f.arr_has), arr_lacks: arr(f.arr_lacks),
                 stem_has: arr(f.stem_has), stem_lacks: arr(f.stem_lacks),
                 lyrics: f.lyrics || '', tunings: arr(f.tunings),
+                mastery: [], match: [],
             };
         }
     }
@@ -263,6 +270,7 @@
         if (f.lyrics) p.set('has_lyrics', f.lyrics);
         if (f.tunings.length) p.set('tunings', f.tunings.join(','));
         if (f.mastery && f.mastery.length) p.set('mastery', f.mastery.join(','));
+        if (f.match && f.match.length) p.set('match', f.match.join(','));
         Object.entries(extra || {}).forEach(([k, v]) => p.set(k, v));
         return p;
     }
@@ -2029,6 +2037,9 @@
             section('Lyrics', ['', '1', '0'].map((v) => '<button data-lyrics="' + v + '" class="px-2 py-1 rounded-md text-xs border ' + (f.lyrics === v ? 'bg-fb-primary text-white border-fb-primary' : 'bg-gray-800/50 text-fb-textDim border-gray-700') + '">' + (v === '' ? 'Any' : v === '1' ? 'Has lyrics' : 'No lyrics') + '</button>').join('')) +
             // Progress (mastery bands) — multi-select; server filters via song_stats.
             section('Progress', [['mastered', 'Mastered'], ['in_progress', 'In progress'], ['not_started', 'Not started']].map((it) => '<button data-mastery="' + it[0] + '" class="px-2 py-1 rounded-md text-xs border ' + (f.mastery.includes(it[0]) ? 'bg-fb-primary text-white border-fb-primary' : 'bg-gray-800/50 text-fb-textDim border-gray-700') + '">' + it[1] + '</button>').join('')) +
+            // Match (P8) — the song's metadata-match lifecycle state, a triage
+            // facet for the enrichment layer. Session-only, like Progress.
+            section('Match', [['review', 'To review'], ['matched', 'Matched'], ['unmatched', 'Unmatched'], ['pending', 'Not scanned']].map((it) => '<button data-match="' + it[0] + '" class="px-2 py-1 rounded-md text-xs border ' + (f.match.includes(it[0]) ? 'bg-fb-primary text-white border-fb-primary' : 'bg-gray-800/50 text-fb-textDim border-gray-700') + '">' + it[1] + '</button>').join('')) +
             section('Tuning', (state.tuningNames || []).map((t) => {
                 // Filter on the server's grouping key (raw offsets for customs)
                 // so two "Custom Tuning" entries are distinct; show their target
@@ -2080,11 +2091,12 @@
             renderDrawer();
             reload();     // re-fetches grid + rail with/without group=1, saves prefs
         });
+        d.querySelectorAll('[data-match]').forEach((b) => b.addEventListener('click', () => { const v = b.getAttribute('data-match'); const i = f.match.indexOf(v); if (i >= 0) f.match.splice(i, 1); else f.match.push(v); renderDrawer(); }));
         d.querySelector('[data-drawer-save]')?.addEventListener('click', saveCurrentAsCollection);
         d.querySelector('[data-drawer-tidy]')?.addEventListener('click', openArtistTidyUp);
         d.querySelector('[data-drawer-close]')?.addEventListener('click', closeDrawer);
         d.querySelector('[data-drawer-clear]')?.addEventListener('click', async () => {
-            state.filters = { arr_has: [], arr_lacks: [], stem_has: [], stem_lacks: [], lyrics: '', tunings: [], mastery: [] };
+            state.filters = { arr_has: [], arr_lacks: [], stem_has: [], stem_lacks: [], lyrics: '', tunings: [], mastery: [], match: [] };
             state.artist = '';
             state.album = '';
             renderDrawer();
@@ -2540,7 +2552,12 @@
             '<div class="max-w-7xl mx-auto px-6 md:px-8 pb-8">' +
             '<div id="v3-songs-toolbar" class="sticky z-20 -mx-6 md:-mx-8 px-6 md:px-8 py-3 mb-4 bg-fb-sidebar/95 backdrop-blur border-b border-fb-border/40">' +
             '<div class="flex flex-col md:flex-row md:items-end justify-between gap-4">' +
-            '<div><p class="text-fb-textDim text-sm" id="v3-songs-count"></p></div>' +
+            // The match-review chip is ambient tool-state (design §11): only
+            // rendered when matches are waiting, silent otherwise. Populated +
+            // shown by match-review.js (window.__fbMatchReviewChip), which
+            // also owns the drawer the click opens.
+            '<div class="flex items-baseline gap-3"><p class="text-fb-textDim text-sm" id="v3-songs-count"></p>' +
+            '<button id="v3-songs-match-review" class="hidden text-xs text-fb-primary hover:text-fb-primaryHi border border-fb-primary/40 rounded-full px-2.5 py-0.5"></button></div>' +
             '<div class="flex flex-wrap gap-2">' +
             (providers.length > 1 ? '<select id="v3-songs-provider" class="' + ctrl + '">' + provOpts + '</select>' : '') +
             '<select id="v3-songs-artist" class="' + ctrl + ' max-w-[11rem]" aria-label="Artist">' + artistSelectHtml() + '</select>' +
@@ -2599,6 +2616,10 @@
         });
         byId('v3-songs-filters').addEventListener('click', openDrawer);
         byId('v3-songs-overlay').addEventListener('click', closeDrawer);
+        // Match-review chip: feature-detected (match-review.js owns the
+        // drawer + the count; absent → the chip just stays hidden).
+        byId('v3-songs-match-review')?.addEventListener('click', () => { if (window.__fbOpenMatchReview) window.__fbOpenMatchReview(); });
+        if (window.__fbMatchReviewChip) window.__fbMatchReviewChip();
         byId('v3-songs-upload').addEventListener('click', () => {
             const legacy = document.getElementById('upload-songs-file');
             // Upload targets the LOCAL library + scan; watchUploadScan refreshes