fix(extraction): self-heal stale halacha 'processing' rows + scheduled drainer

The halacha extraction queue was stuck (same class as the metadata issue): 26
precedents requested extraction with no drainer, plus 1 orphaned in 'processing'
(status=processing, requested_at cleared → never re-picked by the queue).

- db.requeue_stale_processing_extractions(kind): re-stamp orphaned 'processing'
  rows (requested_at IS NULL) so they re-drain; halacha extractor force=False
  resumes from chunk checkpoints (no duplicates).
- process_pending_extractions calls it at the top — fully unattended, safe under
  the global advisory lock. Mirrors the digests-drain self-heal.
- legal-halacha-drain.config.cjs: pm2 cron (every 2h, conservative — Claude is
  slow/rate-limited and each run adds to the chair's pending_review queue).
  drain_halacha_queue.py stays on claude_session (high reasoning quality for
  holding/ratio; NOT moved to Gemini). SCRIPTS.md.

The chair-approval gate (INV-G10) is untouched — this only produces halachot;
Daphna still approves each in /approvals.

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

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

@@ -216,6 +216,16 @@ async def process_pending_extractions(kind: str = "metadata", limit: int = 20) -
     if kind not in {"metadata", "halacha"}:
         raise ValueError("kind must be 'metadata' or 'halacha'")
 
+    # Self-heal stale 'processing' rows (fully unattended): a drain that crashed
+    # mid-extraction can leave a row status='processing' with its requested_at
+    # cleared — orphaned, so it would never be re-picked. Re-stamp it so it
+    # re-drains (the halacha extractor uses force=False → resumes from chunk
+    # checkpoints, no duplicates). Safe under the global advisory lock (only one
+    # drain runs at a time). Mirrors the digests-drain self-heal.
+    healed = await db.requeue_stale_processing_extractions(kind=kind)
+    if healed:
+        logger.warning("self-healed %d stale '%s' processing row(s)", healed, kind)
+
     pending = await db.list_pending_extraction_requests(kind=kind, limit=limit)
     if not pending:
         return {"status": "no_pending", "kind": kind, "processed": 0, "results": []}