getEntriesByType widens to PerformanceEntry; transferSize/
decodedBodySize live on PerformanceResourceTiming (the e2e specs sit
outside tsconfig.build.json, so the bundler never saw this).
A measurement harness, not a pass/fail gate (beyond the mount sanity
it shares with the other lanes): an init-script probe samples the
navigationStart → host-attach latency, a longtask collector runs
through the full built-in tab sweep, sidebar-shaped resource entries
report transfer/decoded/duration, and a frame sampler records the
bottom-strip drag's pacing (p50/p95/max) plus the width-leak guard.
Results print as single-line PERF_JSON records so a shell run can tee
and grep them; before/after comparisons land in
docs/plans/2026-08-31-perf-optimization.md. Baseline (main @ d70db8f,
3 runs): mount ≈ 377ms, 2 longtasks ≈ 161ms, drag p95 = 10ms,
width leak = 504px.
Menghuan1918