fix(ci): duplicate edit and push runs leave cancelled required checks that block merges #597

Problem

Commit Lint and Public Contract Impact run on edited (Public Contract Impact also on labeled and unlabeled) and cancel in-progress runs in a shared concurrency group. When a push and a pull-request body or title edit arrive together, both events start a run on the same head SHA and one of them is cancelled. The cancelled run leaves cancelled check runs for required contexts next to the successful ones.

PR #594 stayed BLOCKED on 2026-10-07 with every required context green: runs 37629187643 (Commit Lint) and 37629187310 (Public Contract Impact) had been cancelled on head 4a792cc. Re-running only those two runs turned the merge state CLEAN. Which of two same-named check runs GitHub treats as current is not documented; the re-run result is the evidence.

It is not a one-off. From 2026-09-15 to 2026-10-07, 9 of 11 cancelled Commit Lint runs and 15 of 20 cancelled Public Contract Impact runs had a run of the same workflow on the same SHA started within 30 seconds. Workflows without edited (Zsh, CodeQL, Trunk, ZD Integration) had none.

Change

Keep the edited and label triggers, because Validate PR Title, Validate Issue Link and the contract label policy need them, but stop these two workflows from producing cancelled runs of required contexts. Both finish in well under a minute, so cancellation saves almost nothing. Set cancel-in-progress: false so a newer event queues behind the running one instead of cancelling it.