🎨 Palette: Improve accessibility of icon-only buttons and toggles

[d3mocide]

🎨 Palette: UX and Accessibility Polish

💡 What: Added essential accessibility attributes (aria-label, aria-pressed, aria-live) and keyboard focus indicators (focus-visible) to several key UI widgets.
🎯 Why: Icon-only buttons (like Play/Pause, Close, Clear Search) were completely invisible to screen readers, and interactive stateful toggles (playback speeds and lookback durations) did not communicate their active states properly to assistive technologies. Keyboard navigation lacked visual clarity. This fulfills my mission as "Palette" to ensure "Accessibility is not optional".
📸 Before/After: See the verification.png attached to the test script output.
♿ Accessibility:

• TimeControls.tsx: Screen readers now announce "Play playback" / "Pause playback", and speed/duration toggles announce their state (aria-pressed).
• SearchWidget.tsx: The clear search ("X") button now has an aria-label, and the results dropdown has aria-label and aria-live="polite" to announce content updates.
• PayloadInspector.tsx: The close button now has an aria-label.
• All affected buttons now feature a distinct focus-visible ring (using hud-green or air-accent) for keyboard users.

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PR created automatically by Jules for task 15812693002069179834 started by @d3mocide

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