fix: static state under prefers-reduced-motion for ApiTagFilter (Gran…

[brooksdevon001-star]

fix: static state under prefers-reduced-motion: reduce for ApiTagFilter (GrantFox FWC26)

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Summary

Implements the ApiTagFilter component with full prefers-reduced-motion: reduce support. When a
user has enabled the OS/browser reduced-motion preference, the hover lift animation (transform:
translateY(-1px)) and CSS transition easing on tag-filter chips are suppressed — chips jump
directly to their final visual state with no movement.

Changes

src/hooks/useReducedMotion.ts (new)
Reusable hook that reads window.matchMedia('(prefers-reduced-motion: reduce)') and subscribes
to live changes, so the value stays in sync if the preference is toggled while the page is
open.

src/pages/ApiTagFilter.tsx (new)
Tag-chip filter bar component. Uses useReducedMotion() to conditionally apply a
tag-chip--no-motion modifier class to every chip when the reduced-motion preference is active.

src/index.css (modified)
Two complementary rules added after the existing .tag-chip block:

• @media (prefers-reduced-motion: reduce) — CSS-level safety net that works regardless of JS
• .tag-chip--no-motion — JS-side mirror applied by the hook for environments where the media
  query may not cascade correctly

src/pages/ApiTagFilter.test.tsx (new)
20 focused tests covering rendering, active/inactive state, click interaction, reduced-motion
behaviour (core of FWC26), and accessibility attributes.

Accessibility

• role="group" + aria-label on the wrapper (WCAG 2.1 AA)
• Each chip is a with aria-pressed for toggle semantics
• Accessible label includes the tag name for screen readers
• Fully keyboard navigable; no disabled attributes

Testing

✓ src/pages/ApiTagFilter.test.tsx (20 tests) — all pass

Notes

FiltersSidebar.tsx has pre-existing unresolved git merge conflict markers that cause the
TypeScript build to fail. This is not introduced by this PR.

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Closes #701