feat(halachot): Phase 6 — deprecate equivalent_halachot writes post-V41

- halacha_batch_reconcile.py --link now exits with error (V41 freezes
  equivalent_halachot; equivalences live in canonical_id instead)
- link_equivalent_halachot emits DeprecationWarning (callers ≥ Python 3.2)
- SCRIPTS.md already marks --link as deprecated; no further doc change needed

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

scripts/halacha_batch_reconcile.py

@@ -93,20 +93,20 @@ async def main(args: argparse.Namespace) -> int:
             w.writerows(pairs)
         print(f"\nreport: {out}", flush=True)
 
-    if args.link and pairs:
-        # #84.2 — record each pair as parallel authority (equivalent_halachot).
-        # Non-destructive: links only, never merges/deletes. Idempotent.
-        linked = 0
-        for p in pairs:
-            if await db.link_equivalent_halachot(
-                p["id_a"], p["id_b"], cosine=p["cosine"],
-                note="cross-precedent parallel authority (halacha_batch_reconcile)",
-                created_by="batch_reconcile",
-            ):
-                linked += 1
-        print(f"linked {linked}/{len(pairs)} pairs as equivalent_halachot", flush=True)
-    elif pairs:
-        print("(review-only — pass --link to record them as equivalent_halachot)", flush=True)
+    if args.link:
+        # V41 (canonical_halachot): equivalent_halachot is FROZEN — no new links.
+        # Use backfill_canonical_halachot.py --apply instead.
+        print(
+            "\nERROR: --link is deprecated since V41 (canonical_halachot model).\n"
+            "  equivalent_halachot is read-only and frozen post-backfill.\n"
+            "  Cross-precedent dedup is now handled by the canonical model:\n"
+            "    mcp-server/.venv/bin/python scripts/backfill_canonical_halachot.py --apply\n"
+            "  Exiting without writing any links.",
+            flush=True,
+        )
+        return 1
+    if pairs:
+        print("(review-only — pair report saved above)", flush=True)
     return 0
 
 
@@ -118,6 +118,6 @@ if __name__ == "__main__":
     ap.add_argument("--include-pending", action="store_true",
                     help="also scan pending_review halachot (default: approved/published only)")
     ap.add_argument("--link", action="store_true",
-                    help="record found pairs as equivalent_halachot (parallel authority, #84.2)")
+                    help="[DEPRECATED since V41] refused at runtime — use backfill_canonical_halachot.py")
     args = ap.parse_args()
     sys.exit(asyncio.run(main(args)))