Self-asserting F1 gate. Results are published to window.__MBB_MATRIX__ so the whole
grid can be read in a single evaluate_script call instead of walked by hand.
<mbb-map> is native MapLibre — the same tag the backend already emits.
Reading this page
It mounts several map widgets a second apart (to stay under the API rate limit), waits ~18s, then self-checks each and prints a pass/fail row.
Green summary = good. Two cells are marked expected-fail and excluded from the score —
they fail on a pre-existing server bug (issue #2276) on both the old and new engines.
Several map instances on one page is heavier than real use; slower paint here is not a defect.