a11y: Tasks 9,13-17 - Settings ARIA, MiniTimer, overlays, ColorPicker, ActivityManager
- Settings: breathing radiogroup/radio, sound aria-pressed, contrast tokens,
placeholder contrast, reset aria-live, abbreviation tags, title tooltips,
back button 44px target
- MiniTimer: paused text #555→#a8a8a8 for AAA contrast
- MicrobreakOverlay: alertdialog role, sr-only heading, aria-describedby
- BreakOverlay: alertdialog role, sr-only heading, aria-label
- ColorPicker: enlarge swatches 22→28px with 44px hit areas, aria-pressed
- ActivityManager: enlarge action buttons to 44px targets, contrast tokens
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