[Fix] Code review checks remain pending after sandboxes stop

[roomote-roomote]

​Opened on behalf of @mrubens. Follow up by mentioning @roomote-roomote, in the web UI, or in Slack.

What changed

• Route PR review sandbox teardown through the centralized terminal finalizer across due sleep, provider timeout, missing sandbox, stale worker, boot failure, and dequeue/bootstrap cancellation paths.
• Keep idle, successfully completed review sessions completed at teardown; cancel non-idle unfinished reviews and explicit stop requests.
• Finalize unfinished canonical review summaries and queued or in-progress GitHub checks when the sandbox can no longer continue the review.
• Preserve a canonical review result and avoid overwriting a check that is already completed.

Why this change was made

PR #1737 exposed a review sandbox that terminated before publishing a result. Several teardown and pre-runtime cancellation paths bypassed the review finalizer, so the canonical summary and GitHub check could remain pending indefinitely.

Impact

Sandbox termination now gives every PR review a terminal GitHub outcome. Successful idle reviews remain completed, explicit stops and non-idle unfinished reviews become canceled, and provider-error recovery behavior for ordinary tasks is unchanged.

[roomote-community]

No new code issues found. See task

• Idle review cancellation records a cancellation sleep-check event.

_{Reviewed 8754257}