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>

scripts/legal-halacha-drain.config.cjs

@@ -0,0 +1,39 @@
+/**
+ * pm2 ecosystem entry for legal-halacha-drain — scheduled drain of the precedent
+ * halacha-extraction queue. Halacha extraction stays on claude_session (local
+ * CLI, high reasoning quality for holding/ratio) — unlike metadata which moved
+ * to Gemini. Extracted halachot land 'pending_review' for the chair's approval
+ * gate (INV-G10); this drainer only produces them, it never approves.
+ *
+ * The drain self-heals orphaned 'processing' rows (precedent_library) and is
+ * serialised by a global advisory lock, so overlapping ticks are safe.
+ *
+ * Pattern: cron_restart fires the script; autorestart:false → one-shot per tick
+ * (pm2 shows "stopped" between ticks). Cheap no-op when the queue is empty.
+ * Cadence is conservative (every 2h) because Claude extraction is slow/rate-
+ * limited and each run adds to the chair's review queue.
+ *
+ * Requires the local ``claude`` CLI + host ~/.env (POSTGRES_URL, etc.).
+ *
+ * Install (once):
+ *     pm2 start /home/chaim/legal-ai/scripts/legal-halacha-drain.config.cjs
+ *     pm2 save
+ * Run now (manual): mcp-server/.venv/bin/python scripts/drain_halacha_queue.py
+ * Schedule override: HALACHA_DRAIN_CRON (default every 2 hours at :47).
+ */
+const cron = process.env.HALACHA_DRAIN_CRON || "47 */2 * * *";
+
+module.exports = {
+  apps: [
+    {
+      name: "legal-halacha-drain",
+      cwd: "/home/chaim/legal-ai",
+      script: "/home/chaim/legal-ai/mcp-server/.venv/bin/python",
+      args: "scripts/drain_halacha_queue.py",
+      env: { HOME: "/home/chaim", PYTHONUNBUFFERED: "1" },
+      autorestart: false, // one-shot per cron tick
+      cron_restart: cron,
+      max_memory_restart: "800M",
+    },
+  ],
+};