v3 library: first-hour polish — zero-states, match progress, provenance, alias search (#730)

* v3 library: first-hour polish — zero-states, match progress, provenance, alias search

Six launch-eve fixes for a brand-new user's first hour with a fresh,
being-matched library. Each is small and reuses shipped idioms.

- Invitational repertoire meter: with no practice data yet, the home meter
  no longer reads "0 of N mastered" (debt framing) — it shows an empty bar
  with "grows as you master songs". A count of 0 read as failure on day one.
- "Start here" starter shelf: growth_edge_suggestions() distinguishes two
  empties — attempts exist but all mastered (honest empty shelf) vs nothing
  attempted yet (day one) → new starter_suggestions() returns up to 8
  approachable songs (90–480s, shortest first) flagged starter:true, and the
  client renders a "Start here" shelf instead of a blank home.
- Library-visible match progress: while the background pass runs, a quiet
  "Matching your library — X of Y" line sits by the review chip (5s poll,
  single guarded interval, cleared the moment the pass stops — no leak,
  no toast, silent completion).
- One-time transparency toast: the first time an install is seen matching a
  real library, one fbNotify names what's contacted (MusicBrainz / Cover Art
  Archive), that results are stored locally, that files aren't changed
  without you, and where the switch is. localStorage-gated, wrapped so a
  blocked notifier can't break the chip.
- Empty-library dead-end card: a genuinely empty local library (no songs, no
  query/filter) shows "Your library is empty" + drop-files hint + Open
  Settings, instead of a bare grid under dead dropdowns.
- Alias-aware search: searching a canonical name ("AC/DC") now also finds
  songs whose raw tag is a merged variant ("ACDC"), via the artist_alias
  table. Probe-guarded so a no-aliases library keeps the exact original
  3-term query; pure predicate, keyset-safe.
- Details-drawer provenance line: matched/manual rows show "Matched:
  <artist — title> (source) · Fix match" under the Identity fields — the
  wrong-match escape hatch at the point of the data, wired to the same
  fix-match flow the card menu uses. New read-only GET
  /api/enrichment/song/{filename} backs it.

Tests: tests/test_starter_suggestions.py (starter vs normal-shelf behaviour,
length window, attempts-exist path unchanged) + alias-search cases added to
tests/test_artist_alias.py. 34 targeted pass; node --check clean; no new
Tailwind classes.

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

* fix(v3 library): stop match-progress poll when leaving the library screen

The 5s enrichment poll (_pollTimer) was cleared on pass completion and on
fetch error, but not when the user navigated away from the library. Leaving
v3-songs mid-pass left the interval pinging /api/enrichment/status in the
background until the pass ended. Subscribe to the existing feedBack
'screen:changed' event: clear the poll when any non-v3-songs screen shows,
and refresh (re-arming if a pass is still running) on returning to v3-songs.

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>

tests/test_artist_alias.py

@@ -209,3 +209,47 @@ def test_list_aliases_sorted(client, server):
     _alias(client, "guns n roses", "Guns N' Roses")
     aliases = client.get("/api/artist-aliases").json()["aliases"]
     assert {a["raw_name"] for a in aliases} == {"ACDC", "guns n roses"}
+
+
+# ── Search (q) matches merged aliases (launch polish) ─────────────────────────
+
+def _search(client, q):
+    return {s["filename"] for s in
+            client.get("/api/library", params={"q": q}).json()["songs"]}
+
+
+def test_search_canonical_finds_raw_variants(client, server):
+    """Searching the canonical name must also find songs whose raw tag is a
+    merged variant — after ACDC→AC/DC, q="AC/DC" returns both."""
+    _seed(server, "a.archive", "ACDC")
+    _seed(server, "b.archive", "AC/DC")
+    _seed(server, "c.archive", "Other")
+    _alias(client, "ACDC", "AC/DC")
+    assert _search(client, "AC/DC") == {"a.archive", "b.archive"}
+
+
+def test_search_partial_canonical_finds_raw_variants(client, server):
+    """The alias term is a LIKE, matching the substring semantics of the
+    plain artist term."""
+    _seed(server, "a.archive", "ACDC")
+    _seed(server, "b.archive", "Other")
+    _alias(client, "ACDC", "AC/DC")
+    assert _search(client, "c/d") == {"a.archive"}
+
+
+def test_search_without_aliases_unchanged(client, server):
+    """No aliases → the fast path keeps the original 3-term search."""
+    _seed(server, "a.archive", "ACDC")
+    _seed(server, "b.archive", "AC/DC")
+    assert _search(client, "ACDC") == {"a.archive"}
+
+
+def test_search_title_album_unaffected_by_alias_term(client, server):
+    """With aliases present (extra placeholder appended), title/album search
+    still works — guards the parameter order."""
+    _seed(server, "a.archive", "ACDC")                       # title "a"
+    _alias(client, "ACDC", "AC/DC")
+    server.meta_db.put("t.archive", 0, 0,
+                       {"title": "Thunder Road", "artist": "Boss", "album": "Born"})
+    assert _search(client, "Thunder") == {"t.archive"}
+    assert _search(client, "Born") == {"t.archive"}