[checkpoint] Restore Harbor agent jobs

Parent

Child of #3222 and #3024. Depends on #3275.

Runtime state

responses_api_agents/harbor_agent/ and responses_api_agents/harbor_agent_general/ owns Ray task references, Harbor job/environment state, trial directory, stable job identity, and terminal result artifacts.

Adapter requirements

Persist the logical execution-to-runtime mapping, provider/version and physical generation, sandbox snapshot/reference, image/spec and mount fingerprints, agent or verifier cursor, and result-manifest identity. Rebind a replacement runtime atomically and fence the old handle. Never claim that a filesystem-only copy restores unsupported live process state.

Acceptance criteria

• Restore reattaches or consumes the existing trial without launching a second job; running, partial, and terminal phases are distinct.
• Mutate runtime state, commit, replace both application and runtime process where supported, restore, and compare the next operation/result.
• Stale handles and delayed old-runtime results are rejected.
• Partial restore activates no execution mapping.
• Duplicate retirement and failed-provider cleanup release the restored runtime exactly once.

Start with responses_api_agents/harbor_agent/ and responses_api_agents/harbor_agent_general/, then read the parent issues #3222 and #3024 and dependency #3275. Trace how Ray task references, Harbor state, trial directories, runtime identity, and terminal artifacts are currently managed. Done means restore distinguishes running, partial, and terminal phases, rejects stale results, and releases restored runtimes exactly once without launching duplicate jobs.