feat: correlate bca terminal readback to exact receipt tuple

[CondorCommodore]

Summary

• verify BCA terminal readback against the exact immutable reservation tuple
• require correlated chains to preserve the same durable correlation object across reservation and receipt events
• extend coordinator/tests to pass and enforce the exact expected correlation tuple

Testing

• ./.venv/bin/ruff check scripts/c2_coord_client.py scripts/cos_assignment_coordinator.py tests/test_c2_coord_client.py tests/test_cos_assignment_coordinator.py
• python3 -m pytest -q tests/test_c2_coord_client.py tests/test_cos_assignment_coordinator.py tests/test_cos_dispatch_orchestrator.py tests/test_cos_worker_receipt_adapter.py tests/test_cos_bootstrap_supervisor.py

[chatgpt-codex-connector]

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[chatgpt-codex-connector]

Derive correlation fields instead of indexing the envelope

Every real dispatch_task call passes json.loads(envelope.canonical_json()), but a DispatchEnvelope contains coord_session_id rather than session_id and has no payload_digest; the latter is computed only inside reserve_bca. Consequently this comprehension raises KeyError('session_id') after the edge dispatch and worker receipt have already occurred, so terminal readback never runs. Build the correlation tuple using the same session mapping and digest calculation as the reservation payload.

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