feat(ui): D.6c rename local SectionHeader to NumberedSectionToggle

[slittycode]

Summary

PR 10 (sub-step c) of 16. Last of three small PRs against MeasurementDashboard.tsx — closes out the dashboard migration.

The local SectionHeader at :293 is structurally a collapsible toggle button (the whole row IS the click target for open/close), not a static <h2> like the ui/SectionHeader primitive. Substituting the primitive would either nest interactive elements or swallow the collapsibility, so the local component stays — but it gets renamed to NumberedSectionToggle so the distinction is obvious and the name no longer shadows the primitive.

Also tightens the a11y of the toggle: adds aria-expanded={isOpen} on the button and aria-hidden on the +/− glyph (purely decorative once aria-expanded carries the state).

Preserved verbatim

• data-text-role="meta" + data-text-role="section-title" attributes (analysisResultsUi.test.ts spec-level vocabulary).
• All call sites — only the local component name changes; the props and behavior are unchanged.
• All Section IDs / data-testid hooks (rhythm-grid-*, spectral-*).

Test plan

• npm run lint — clean
• npm run test:unit — 628/628 passing
• npm run test:smoke — sandbox blocks Playwright browser; data-testids + text + ARIA preserved

Status

D.6 (MeasurementDashboard) is now fully migrated across 10a / 10b / 10c.

Up next

D.7 — SessionMusicianPanel + MixDoctorPanel.

https://claude.ai/code/session_01WNtYcWXwn4mVnnjxqT7uAe

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[slittycode]

Verdict: APPROVE

Summary

Renames the local SectionHeader component in MeasurementDashboard.tsx to NumberedSectionToggle and adds aria-expanded/aria-hidden a11y attributes. One file, 20 lines. The rename is complete — no orphaned call sites remain, and the only surviving SectionHeader references in the file are in the comment explaining the architectural distinction. The JSDoc comment correctly records why the local component cannot be replaced by the ui/SectionHeader primitive. Unit tests are reported 628/628 passing.

Findings

Worth considering:
NumberedSectionToggle now has aria-expanded but no aria-controls pointing at the controlled section div. Screen readers will announce the expanded/collapsed state but can't programmatically navigate to the revealed content. Not a regression (the previous code had neither), but since you're touching a11y anyway, wiring aria-controls to the section's data-testid id would complete the pattern.

Test results

628/628 unit passing per PR description. CI checks were in-progress at review time; the diff touches no logic — only a rename and two attribute additions — so a CI failure here would be environmental, not caused by this change.

Phase boundary check

Clean. No Phase 1, Phase 2, or Phase 3 code touched.

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Generated by Claude Code