[parked] perf(UnderlineNav): replace JS DOM measurement with CSS overflow + IntersectionObserver#7541

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hectahertz wants to merge 23 commits intomainfrom

hectahertz/perf/underlinenav-intersection-observer-overflow

Commits on Feb 13, 2026

Commits on Feb 14, 2026

fix(UnderlineNav): address review feedback
hectahertz
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test(UnderlineNav): add IO/RO mock tests for overflow detection
hectahertz
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test(vrt): update snapshots

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github-actions[bot]
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fix(UnderlineNav): use CSS anchor positioning for More button placement
hectahertz
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Revert "test(vrt): update snapshots"
hectahertz
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fix(UnderlineNav): reserve space for More button via IO rootMargin
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chore(UnderlineNav): clean up stale comments and simplify AnchorMarker CSS
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fix(UnderlineNav): prevent flicker during resize by deferring overflow clear during icon retry
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refactor(UnderlineNav): extract overflow observer into documented helper functions
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fix(UnderlineNav): add stylelint-disable for CSS anchor positioning
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docs(UnderlineNav): clarify icon toggle state machine diagram
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Commits on Feb 16, 2026

Commits on Feb 18, 2026