Plan item B4. performance-ratchet.yml measures master on three runners
(initial bytes and the journeys) and tighten-baselines.mjs lowers every
baseline that all three runs beat, opening a no-release-note PR only when
the file changed. The journeys steps move into a composite action shared
with ci.yml's Performance journeys job.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
