The Playwright run produces error-context.md per failed test
with a full DOM snapshot — useful for triaging UI test failures
without round-tripping through downloaded artifacts. Cat it
into the workflow log on failure.
Also bump actions/upload-artifact v3 → v4. v3 uploads still
return success on this Gitea runner but the artifacts don't
surface through the API or UI; v4 is the correct version per
the workflow header note.
steve
68276810ec