fix(halachot): exclude embedding from update_halacha RETURNING

PATCH /api/halachot/{id} was returning 500 because the row included
``embedding`` as a numpy.ndarray of np.float32, which FastAPI's
jsonable_encoder cannot serialize (vars() and dict() both fail on it).

The bug had been latent — it triggered for the first time today after
the auto-approve batch left only low-confidence halachot for the chair
to review manually, and her first PATCH hit the unserializable response.

Replace ``RETURNING *`` with an explicit column list (everything except
``embedding``). Callers that need the embedding can re-fetch via
``get_halacha`` — but no current caller does.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

mcp-server/src/legal_mcp/services/db.py

@@ -2096,7 +2096,17 @@ async def update_halacha(
     if not set_parts:
         return None
     set_parts.append("updated_at = now()")
-    sql = f"UPDATE halachot SET {', '.join(set_parts)} WHERE id = $1 RETURNING *"
+    # Exclude `embedding` — it's a numpy.ndarray of np.float32 that breaks
+    # FastAPI's jsonable_encoder downstream (PATCH /api/halachot/{id}).
+    # Callers that need it (none today) can re-fetch with get_halacha.
+    sql = f"""
+        UPDATE halachot SET {', '.join(set_parts)} WHERE id = $1
+        RETURNING id, case_law_id, halacha_index, rule_statement, rule_type,
+                  reasoning_summary, supporting_quote, page_reference,
+                  practice_areas, subject_tags, cites, confidence,
+                  quote_verified, review_status, reviewer, reviewed_at,
+                  created_at, updated_at
+    """
     row = await pool.fetchrow(sql, *params)
     return dict(row) if row else None