feat(enrichment): loose MusicBrainz search fallback (find aliased/romanized artists) (#771)

* feat(enrichment): loose MusicBrainz search fallback (find aliased artists)

The MB text search used a strict field-phrase query
(`recording:"<title>" AND artist:"<artist>"`). A field phrase only matches
MusicBrainz's *primary* artist/title — it never searches ALIASES — so a
recording stored under a non-Latin primary name (大橋純子) whose romanized
form ("Junko Ohashi") is only an alias returns ZERO results, even though MB
has it. Whole swaths of a community library (e.g. romanized J-pop / city-pop
charts) were unsearchable.

- `build_recording_query(..., loose=True)` drops the field scoping + phrases
  for plain AND-ed term groups (`(telephone number) AND (junko ohashi)`),
  which searches the whole document incl. aliases.
- `_mb_search_recordings` runs the strict query first (unchanged, high
  precision) and only on an EMPTY result retries once with the loose query —
  so mainstream matches are untouched and the extra throttled request is spent
  only on a miss. Results are re-scored by rank_candidates, so recall goes up
  without lowering match quality (auto-accept still needs the per-field floors).

Verified live: "Junko Ohashi / Telephone Number" and "Anri / Windy Summer"
(both 0 under the strict query) now surface the real records; "AC/DC /
Highway to Hell" still hits strict at score 1.0 with no loose retry.

Follow-up (separate): alias-aware SCORING so these can auto-confirm, not just
appear as manual candidates.

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

* fix(enrichment): keep live exclusion in the loose search fallback

The loose fallback dropped the strict path's -secondarytype:Live filter, so a
studio chart whose strict query missed could fall back to — and, since
score_candidate doesn't penalize live takes, auto-confirm — a live-only
recording. Apply the same live gate to the loose query (skipped only when the
source title is itself a live take).

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

---------

Co-authored-by: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Co-authored-by: byrongamatos <xasiklas@gmail.com>

server.py

@@ -6320,15 +6320,30 @@ def _mb_http_get(path: str, params: dict) -> dict | None:
 
 
 def _mb_search_recordings(artist, title, limit: int = 12) -> list[dict]:
-    """Text search (tier 2–4): denoised Lucene query over /recording. The query
-    now drops live-only recordings and our ranker rewards the studio take, so a
+    """Text search (tier 2–4): denoised Lucene query over /recording. The strict
+    query drops live-only recordings and the ranker rewards the studio take, so a
     slightly larger default result set gives the re-ranker room to surface the
-    canonical version (one request per song regardless of limit)."""
+    canonical version.
+
+    Runs the strict field-phrase query first (high precision); if it finds
+    nothing, retries ONCE with a loose term query. The strict phrase only matches
+    MusicBrainz's *primary* artist/title, so a recording stored under a non-Latin
+    primary name (大橋純子) whose romanized form ("Junko Ohashi") is only an alias
+    is invisible to it — the loose query searches aliases and rescues it. The
+    retry spends a second throttled request only on a miss; results are re-scored
+    by rank_candidates, so the looser recall doesn't lower match quality
+    (auto-accept still needs the per-field floors)."""
     query = mb_match.build_recording_query(artist, title)
-    if not query:
-        return []
-    body = _mb_http_get("recording", {"query": query, "limit": limit})
-    return mb_match.parse_search_response(body or {})
+    cands: list[dict] = []
+    if query:
+        body = _mb_http_get("recording", {"query": query, "limit": limit})
+        cands = mb_match.parse_search_response(body or {})
+    if not cands:
+        loose = mb_match.build_recording_query(artist, title, loose=True)
+        if loose and loose != query:
+            body = _mb_http_get("recording", {"query": loose, "limit": limit})
+            cands = mb_match.parse_search_response(body or {})
+    return cands
 
 
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