rfdb-stale-node-cleanup

Recover from stale RFDB nodes that survive commit_batch cleanup despite having their file field listed in changed_files. Use when: (1) re-running an enricher/orchestrator step but old data with the same file field stays in the graph, (2) commit_batch(changed_files=[X], ...) reports success but a query later still returns nodes with file = X, (3) you re-pointed structural nodes (e.g., DIRECTORY/FILE) from a synthetic…