Fix IPFS CID detection in legacy_tasks node caching

- Rename misleading ipfs_cid variable to content_cid
- Detect IPFS CIDs by prefix (Qm or bafy) instead of truthy check
- Add clearer logging to show whether IPFS or local hash is used

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

legacy_tasks.py

@@ -354,15 +354,20 @@ def execute_dag(self, dag_json: str, run_id: str = None) -> dict:
                 cache_node_type = "dag_intermediate"
 
             # Store in cache_manager (indexes by cid, uploads to IPFS)
-            cached, ipfs_cid = cache_manager.put(
+            # put() returns (CachedFile, cid) where cid is IPFS CID if available, else local hash
+            cached, content_cid = cache_manager.put(
                 Path(node_path),
                 node_type=cache_node_type,
                 node_id=node_id,
             )
-            node_hashes[node_id] = ipfs_cid or cached.cid  # Prefer IPFS CID
-            if ipfs_cid:
-                node_ipfs_cids[node_id] = ipfs_cid
-            logger.info(f"Cached node {node_id}: {cached.cid[:16]}... -> {ipfs_cid or 'no IPFS'}")
+            # content_cid is the primary identifier (IPFS CID or local hash)
+            node_hashes[node_id] = content_cid
+            # Track IPFS CIDs separately (they start with Qm or bafy)
+            if content_cid and (content_cid.startswith("Qm") or content_cid.startswith("bafy")):
+                node_ipfs_cids[node_id] = content_cid
+                logger.info(f"Cached node {node_id}: IPFS CID {content_cid}")
+            else:
+                logger.info(f"Cached node {node_id}: local hash {content_cid[:16] if content_cid else 'none'}...")
 
     # Get output hash from the output node
     # Use the same identifier that's in the cache index (IPFS CID if available)