fix(discover): hide stale singles + replace album set on re-derive

- Client filters the row's album thumbnails to full albums only (hides
  singles/EPs left over from pre-albums-only sweeps).
- Worker: re-deriving an artist deletes its pending album suggestions that are
  no longer picks (stale singles / now-owned), keeping wanted/dismissed rows,
  so the suggestion set self-cleans instead of accumulating.

worker 246, web 189 tests.

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

worker/lyra_worker/discovery.py

@@ -217,6 +217,16 @@ def _derive_albums(conn: psycopg.Connection, browser: MbBrowser, surfaced: list[
         if popular is not None:
             reasons[popular] = "newest,popular" if reasons.get(popular) == "newest" else "popular"
 
+        # Re-deriving replaces this artist's album set: drop any pending album suggestion of
+        # theirs that is no longer a pick (stale singles/EPs from older sweeps, or an album now
+        # owned), keeping wanted/dismissed rows untouched. Then upsert the current picks.
+        with conn.cursor() as cur:
+            cur.execute(
+                "DELETE FROM \"DiscoverySuggestion\" WHERE kind = 'album' AND status = 'pending' "
+                'AND "artistMbid" = %s AND NOT ("rgMbid" = ANY(%s))',
+                (artist["mbid"], list(reasons.keys())),
+            )
+
         for rg in core:  # preserve newest-first order among the chosen
             reason = reasons.get(rg.rg_mbid)
             if reason is not None:

worker/tests/test_discovery_albums.py

@@ -2,7 +2,7 @@ from lyra_worker.adapters.fakes import FakeMbBrowser, FakeSimilaritySource
 from lyra_worker.browser import ReleaseGroupInfo
 from lyra_worker.discovery import DiscoveryConfig, run_discovery
 from lyra_worker.similarity.base import SimilarArtist
-from tests.conftest import insert_monitored_release, insert_watched_artist
+from tests.conftest import insert_discovery_suggestion, insert_monitored_release, insert_watched_artist
 
 
 def _album_rows(conn):
@@ -92,6 +92,34 @@ def test_popular_matches_by_title_when_lastfm_mbid_missing_and_skips_owned(conn)
     assert _reasons(conn) == {"rg-new": "newest", "rg-match": "popular"}
 
 
+def test_rederiving_replaces_stale_pending_album_suggestions(conn):
+    insert_watched_artist(conn, mbid="s1", name="Seed")
+    # a stale pending album suggestion for c1 that is no longer a pick (e.g. an old single)
+    insert_discovery_suggestion(conn, kind="album", artist_mbid="c1", rg_mbid="rg-old-single",
+                                album="Old Single", status="pending")
+    src = FakeSimilaritySource(similar={"s1": [SimilarArtist("c1", "Cand", 0.9)]})
+    browser = FakeMbBrowser(releases={"c1": [
+        ReleaseGroupInfo("rg-new", "New Album", "Album", (), "2022-01-01"),
+    ]})
+    run_discovery(conn, [src], browser, DiscoveryConfig(albums_per_artist=1))
+    # the stale single is gone; only the freshly-derived album remains
+    assert [r[1] for r in _album_rows(conn)] == ["rg-new"]
+
+
+def test_rederiving_keeps_wanted_album_suggestions(conn):
+    insert_watched_artist(conn, mbid="s1", name="Seed")
+    insert_discovery_suggestion(conn, kind="album", artist_mbid="c1", rg_mbid="rg-wanted",
+                                album="Wanted One", status="wanted")
+    src = FakeSimilaritySource(similar={"s1": [SimilarArtist("c1", "Cand", 0.9)]})
+    browser = FakeMbBrowser(releases={"c1": [
+        ReleaseGroupInfo("rg-new", "New Album", "Album", (), "2022-01-01"),
+    ]})
+    run_discovery(conn, [src], browser, DiscoveryConfig(albums_per_artist=1))
+    with conn.cursor() as cur:  # wanted row untouched (only pending stale rows are replaced)
+        cur.execute('SELECT count(*) FROM "DiscoverySuggestion" WHERE "rgMbid" = %s AND status = \'wanted\'', ("rg-wanted",))
+        assert cur.fetchone()[0] == 1
+
+
 def test_no_popularity_provider_yields_newest_only(conn):
     insert_watched_artist(conn, mbid="s1", name="Seed")
     src = FakeSimilaritySource(similar={"s1": [SimilarArtist("c1", "Cand", 0.9)]})