A merged or closed pull's queued checks are cancelled: six orphans held the lane for two hours today #1239

At 14:45Z the check lane (one at a time, ~20 min each) held 47 queued checks; six of them belonged to pulls already merged (#1167, #1168, #1191, #1192, #1207, #1210): the second check the forge queues on approval, left behind when the person landed the pull. Two hours of lane for nothing. Cancelled by hand.

Done looks like:

• [ ] When a pull is merged or closed, every queued or running check and deploy run for it is cancelled with the summary pull landed / pull closed (src/crew or src/checks where the merge and close actions live).
• [ ] The approval re-check is not queued at all when the pull's head already passed its check on the same base (the approval was on that green); it is queued only when the base moved (#1133).
• [ ] test/checks.test.ts (or the pulls test): merging a pull with a queued check leaves no queued run for it.

Evidence: GET /api/v1/repos/trevato/forge/runs at 14:45Z, 2026-10-13.