Document Stalled Copilot Review Request Recovery

[ptr727]

Problem

scripts/pr_review.py status detects a Copilot request that was never picked up and instructs the agent to "clear the request and re-request, per the runbook." The GitHub Copilot Review Runbook in .github/copilot-instructions.md does not document how to perform either mutation.

The script itself can add a request through wait, but it deliberately skips that mutation while the reviewer remains in the pending request set. It has no command that clears a stalled request.

Observed evidence

Promotion PR #867 reported REQUEST NOT PICKED UP with no copilot_work_started event. Reading the named runbook found no clear-and-re-request procedure. Recovery required discovering and running these provider-specific commands outside the documented path:

gh pr edit <pr> --repo <owner/repo> --remove-reviewer copilot-pull-request-reviewer
gh pr edit <pr> --repo <owner/repo> --add-reviewer copilot-pull-request-reviewer

Expected behavior

Either scripts/pr_review.py should own a safe recovery command that resolves all identifiers live, or the runbook should document the exact supported commands. The status output must point to a procedure that exists so an unattended review loop does not stop on an incomplete instruction.

[ptr727]

Additional evidence from PR #873:

• Four ordinary Copilot requests produced no copilot_work_started timeline event.
• pr_review.py wait therefore terminated each time with REQUEST_NOT_PICKED_UP.
• GitHub displayed the final request as converted to a "lite review" and removed the ordinary Copilot request.
• About four minutes later, a normal COMMENTED review appeared on the same head SHA with full 13/13-file coverage and 12 inline comments.
• Once the review existed, pr_review.py status parsed it correctly as one full round with 12 unresolved threads.

The missing piece is liveness handling: a lite-review conversion can complete without a copilot_work_started event, after the current waiter has already declared the request dead. The reader works after completion; the pickup/stall model does not recognize this request shape.