* Curate the highlight.js build to ~29 languages (lib/core + the
common set) instead of the full ~190-grammar default: -787 KB raw /
-230 KB gz on the base bundle.
* Code-split every route via React.lazy with a per-layout <Suspense>
in App.jsx so the sidebar stays mounted on navigation. Initial entry
chunk drops from 3194 KB raw / 887 KB gz to 397 KB / 122 KB (-87%).
Warm chunks on sidebar hover/focus/touch via a preload registry so
the click finds the chunk already in flight or cached.
* Migrate Playwright coverage from istanbul (build-time counters) to
native Chromium V8 coverage, with per-worker accumulation +
conversion. Suite drops from 71s to 30s at 20 workers (~58%) at the
non-instrumented floor.
* Keep the coverage gate bundling-invariant: the coverage build inlines
dynamic imports so every shipped source file lands in the denominator
(otherwise untested page chunks silently drop out and inflate the
percentage). Production builds stay code-split.
* Add UI_TEST_WORKERS=N Makefile knob; tighten coverage tolerance to
0.8pp now that jitter sits near istanbul's ~0.5pp again.
Assisted-by: Claude:claude-opus-4-7 [Claude Code]
Signed-off-by: Richard Palethorpe <io@richiejp.com>
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