Body edits cancel required check runs and leave PRs BLOCKED; rerun replays stale payloads #5159

Problem

Editing a PR body, for example to rebind the routine marker, fires pull_request: edited. Workflows with cancel-in-progress concurrency then cancel the in-flight or completed runs for the same head.

• GitHub treats a required check whose latest run was cancelled as failing, so the PR shows BLOCKED although every check passed.
• Re-running a cancelled run replays the old event payload, so body-reading checks (routine-eligibility, declared-closes) then fail on the stale marker.
• This blocked coord: the board-v2 tend writer, allowlisted and item-scoped, with C1 close and gate replay behind the enable file (Refs #5136) #5158 for over an hour on 2026-11-01 and has recurred on many PRs (routine-delivery: pre-enforce controls for the board gate (Refs #5094) #5115, coord: accept a strict PR that Refs one open native sub-issue Delivery of its item (Refs #5100) #5138, skills: strict-item-lifecycle drops its closing-linkage exception (Refs #5100) #5145).

Done when

• Required workflows don't cancel another event's run for the same head SHA. Concurrency groups are keyed by head SHA plus event (or edited runs never cancel synchronize runs), or body-reading checks run in their own workflow with their own group.
• A body-only edit leaves every non-body required check's latest run green.
• There is a fixture or test proving the concurrency keys.

Filed by Root/fdev as a process improvement. Refs #5097