Fix plan storage path to match get_by_cid lookup

Store plan directly in CACHE_DIR/{cid} instead of CACHE_DIR/legacy/{cid},
which matches what cache_manager.get_by_cid() checks at line 396-398.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

legacy_tasks.py

@@ -392,7 +392,7 @@ def execute_dag(self, dag_json: str, run_id: str = None) -> dict:
         import asyncio
         import database
 
-        # Store plan (DAG) to IPFS
+        # Store plan (DAG) to IPFS and local cache
         plan_cid = None
         try:
             import ipfs_client
@@ -400,6 +400,12 @@ def execute_dag(self, dag_json: str, run_id: str = None) -> dict:
             plan_cid = ipfs_client.add_json(dag_dict)
             if plan_cid:
                 logger.info(f"Stored plan to IPFS: {plan_cid}")
+                # Also store locally so it can be retrieved without IPFS
+                # Store directly in cache_dir (get_by_cid checks cache_dir/cid)
+                plan_path = CACHE_DIR / plan_cid
+                CACHE_DIR.mkdir(parents=True, exist_ok=True)
+                with open(plan_path, "w") as f:
+                    json.dump(dag_dict, f, indent=2)
         except Exception as e:
             logger.warning(f"Failed to store plan to IPFS: {e}")