fix(ci): stop pushes to main cancelling each other's verify run

[wormeyman]

Found while verifying the merge queue from tonight: two main runs came back cancelled rather than green.

commit	PR	main run
5f676ea	#51	success
605a4cc	#52	cancelled
be5f592	#59	cancelled
0e484c0	#55	success
336dd2a	#57	success

Cause is the concurrency block from #56. cancel-in-progress: true with a group keyed on github.ref is correct for pull requests - a superseded push to a PR branch is ~4 minutes of waste - but on main it means a second merge kills the first one's run. Six PRs merged inside half an hour tonight, so two commits on the deploy branch have no verdict of their own.

Why it matters, stated honestly

Neither commit is unverified in practice. Each had a green verify on its own PR, and ruleset EJ will not let anything merge without one.

But "green on the PR" and "green as it sits on main" are different claims. strict_required_status_checks_policy is false (see #60), so a branch need not be current with main to merge - which means a PR check can pass against an older tree than the one that ends up on main. That is not theoretical here: #56 changed vite.config.ts and #52 changed what verify itself means by adding a check:vue phase, both within the same hour. A main run is the only thing that checks the combination as shipped, and main is what deploy ships from.

The change

cancel-in-progress: ${{ github.event_name == 'pull_request' }}

Gated on the event rather than on the ref, so it keeps cancelling for pull_request, stops for push, and stays correct if a push trigger is ever added for another branch.

Cost: back-to-back merges now each get a ~4 minute run instead of one. That is the point.

Verification

pnpm vp check clean locally (316 files formatted, 301 files no warnings/lint/type errors). CI verify runs on this PR - and note the PR run itself exercises the pull_request side of the new expression, so a green check here proves cancelling still works where it should. The push side only demonstrates itself on the next pair of rapid merges.

Not addressed here: #60 (whether to make status checks strict, which would close the underlying gap directly) and #61 (pnpm vp build absent from CI).

🤖 Generated with Claude Code

https://claude.ai/code/session_01F3a2HLJ4beKARi7SPmaM54