Verify deadline expiry after cancellation-swallowing cleanup

A cancellation-based deadline can return normally if dependency cleanup suppresses cancellation. Do not infer timely success from normal context-manager exit: inspect the deadline's expiry state after cleanup, and separately preserve pending external cancellation. For a monitoring sweep, update its completion timestamp only after those guards; an incomplete sweep must retain previous completion evidence. Exercise real connection, invocation and teardown boundaries, including a dependency that catches cancellation. The deadline requests cancellation rather than forcibly stopping non-cooperative work; shielded cleanup may add overhead, so distinguish the operation budget from a hard wall-clock cutoff.

Applies when: Asynchronous session cleanup can absorb cancellation used for deadlines or task shutdown. Keywords: timeout deadline teardown cleanup swallowed cancellation false success timestamp