Fix embedding dimensions and worker session management

Two issues:
1. CLAP model output needed .flatten() to produce a 1-D vector for
   pgvector. Without it, the nested array caused "expected ndim to be 1".
2. Worker now uses a fresh session per track instead of sharing one
   across a batch, preventing PendingRollbackError cascading from one
   failure to the next.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

src/haunt_fm/services/embedding.py

@@ -44,7 +44,7 @@ def embed_audio(audio: np.ndarray, sample_rate: int = 48000) -> np.ndarray:
     with torch.no_grad():
         embeddings = _model.get_audio_features(**inputs)
 
-    # Normalize
-    emb = embeddings[0].numpy()
+    # Flatten to 1-D and normalize
+    emb = embeddings[0].numpy().flatten()
     emb = emb / np.linalg.norm(emb)
     return emb

src/haunt_fm/services/embedding_worker.py

@@ -26,29 +26,30 @@ def last_processed() -> datetime | None:
     return _last_processed
 
 
-async def _process_track(session: AsyncSession, track: Track) -> bool:
+async def _process_track(track_id: int, artist: str, title: str, preview_url: str | None) -> bool:
     """Process a single track: find preview, download, embed, store. Returns True on success."""
     global _last_processed
 
+    async with async_session() as session:
         # Mark as downloading
         await session.execute(
-        update(Track).where(Track.id == track.id).values(embedding_status="downloading")
+            update(Track).where(Track.id == track_id).values(embedding_status="downloading")
         )
         await session.commit()
 
         # Find iTunes preview
-    if not track.itunes_preview_url:
-        result = await search_track(track.artist, track.title)
+        if not preview_url:
+            result = await search_track(artist, title)
             if result is None:
                 await session.execute(
-                update(Track).where(Track.id == track.id).values(embedding_status="no_preview")
+                    update(Track).where(Track.id == track_id).values(embedding_status="no_preview")
                 )
                 await session.commit()
                 return False
 
             await session.execute(
                 update(Track)
-            .where(Track.id == track.id)
+                .where(Track.id == track_id)
                 .values(
                     itunes_track_id=result["track_id"],
                     itunes_preview_url=result["preview_url"],
@@ -59,11 +60,9 @@ async def _process_track(session: AsyncSession, track: Track) -> bool:
             )
             await session.commit()
             preview_url = result["preview_url"]
-    else:
-        preview_url = track.itunes_preview_url
 
         # Download and decode
-    filename = f"{track.id}.m4a"
+        filename = f"{track_id}.m4a"
         filepath = await download_preview(preview_url, settings.audio_cache_dir, filename)
         audio = decode_audio(filepath)
 
@@ -72,12 +71,12 @@ async def _process_track(session: AsyncSession, track: Track) -> bool:
 
         # Store
         track_embedding = TrackEmbedding(
-        track_id=track.id,
+            track_id=track_id,
             embedding=embedding.tolist(),
         )
         session.add(track_embedding)
         await session.execute(
-        update(Track).where(Track.id == track.id).values(embedding_status="done")
+            update(Track).where(Track.id == track_id).values(embedding_status="done")
         )
         await session.commit()
 
@@ -109,27 +108,31 @@ async def run_worker():
                         .order_by(Track.created_at)
                         .limit(settings.embedding_batch_size)
                     )
-                    tracks = result.scalars().all()
+                    tracks = [
+                        (t.id, t.artist, t.title, t.itunes_preview_url)
+                        for t in result.scalars().all()
+                    ]
 
                 if not tracks:
                     await asyncio.sleep(settings.embedding_interval_seconds)
                     continue
 
-                    for track in tracks:
+                for track_id, artist, title, preview_url in tracks:
                     try:
-                            await _process_track(session, track)
-                            logger.info("Embedded: %s - %s", track.artist, track.title)
+                        await _process_track(track_id, artist, title, preview_url)
+                        logger.info("Embedded: %s - %s", artist, title)
                     except Exception as e:
-                            logger.exception("Failed to embed %s - %s", track.artist, track.title)
-                            await session.execute(
+                        logger.exception("Failed to embed %s - %s", artist, title)
+                        async with async_session() as err_session:
+                            await err_session.execute(
                                 update(Track)
-                                .where(Track.id == track.id)
+                                .where(Track.id == track_id)
                                 .values(
                                     embedding_status="failed",
                                     embedding_error=str(e),
                                 )
                             )
-                            await session.commit()
+                            await err_session.commit()
 
             except Exception:
                 logger.exception("Embedding worker error")