Report the shot at the commit that has a branch

[abernier]

Groundwork for adding UI Tests to the branch ruleset. It cannot be added today: the status never reaches the commit a required check is read from.

Chromatic posts UI Tests and UI Review on whatever commit the CLI is handed, and on a pull_request event that is GITHUB_SHA -- the merge commit GitHub builds for the run, a commit that exists on no branch. GitHub Actions, by contrast, reports its check runs on the head commit. Measured on #187, they never meet:

$ gh api repos/pmndrs/examples/commits/5520f5f2/check-runs --jq '.total_count'   # head
12
$ gh api repos/pmndrs/examples/commits/5520f5f2/status --jq '.statuses | length'
0

$ gh api repos/pmndrs/examples/commits/aefcbe4/status --jq '.statuses[] | "\(.context)\t\(.state)"'   # merge commit
Test suite publish  success
UI Tests            pending
UI Review           pending

The pull request shows all of them together -- GitHub knows the merge commit is its -- so nothing looks wrong until you make one of them required, at which point every pull request waits forever on a status that lands somewhere else.

So hand Chromatic the head commit explicitly, plus the branch and slug that have to travel with it or the build attaches to the wrong ref. All three are empty on a push, where GITHUB_SHA is already the commit itself.

After this merges

1. Re-run chromatic-job on an open pull request and check the status lands on the head:

   gh api repos/pmndrs/examples/commits/$(gh pr view 187 --json headRefOid --jq .headRefOid)/status \
     --jq '.statuses[] | "\(.context)\t\(.state)"'

2. Only then add UI Tests to the Basic ruleset as a required status check.

🤖 Generated with Claude Code