[checkpoint] Enable Indian Banking Gymnasium snapshots #3239

Parent

Child of #3219 and #3024.

Problem and state owner

resources_servers/indian_banking/app.py owns the synthetic banking world/database, task, dialogue history, and turn counters in generic Gymnasium session state.

Proposed adapter

Explicitly opt in only after validating the complete world state is JSON-safe and engine globals are reconstructible.

Implement explicit checkpoint opt-in, route classification, export/restore/retire hooks, execution-to-session binding, revision reporting, atomic replacement under attempt N+1, and stale-attempt fencing.

Acceptance criteria

• Tool mutations and dialogue turns continue without cross-session leakage; cached judge/simulator state is not silently shared.
• Checkpoint after multiple mutations, replace the server process, restore, and compare the next operation with an uninterrupted execution.
• Corrupt or incomplete bulk state activates no sessions.
• Attempt N cannot mutate or retire restored attempt N+1.
• Terminal cleanup is idempotent and releases restored state exactly once.