[Fix] Task runs complete twice after duplicate terminal events

[roomote-roomote]

Opened on behalf of Daniel Riccio. View the task or mention @roomote-roomote for follow-up asks.

What changed

• Made settled harness completion idempotent so replayed terminal events cannot emit duplicate run-exit and completed updates.
• Added regression coverage for hidden queued re-review turns across paired OpenCode idle events, including exactly-once run completion.
• Added sequential notification coverage for live-heartbeat deferral, stale/dead-worker release, replacement-worker settlement, and retry delivery without duplicate posts.

Why this change was made

The fixes in #1157 and #1170 covered paired idle handling and stale-heartbeat notification release independently. Exercising those paths as lifecycle sequences exposed that a duplicate terminal event could still finalize an already settled harness turn twice.

Impact

Live turns retain the existing debounce and deferral behavior, including during replacement-worker recovery. Pending review feedback is released after a dead worker and delivered once, while each real harness turn now produces one run completion even if its terminal event is replayed. Focused worker and BullMQ lifecycle suites, package typechecks, formatting, and the repository pre-push checks pass.

[roomote-community]

No code issues found. See task

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