fix: add escape-to-dismiss and focus pause to toast notifications

[edrizxabdulganiyu-blip]

fix: keyboard accessibility for toast notifications

Summary

Toast notifications were only dismissible by clicking "Close" or waiting for the timer. A
keyboard user focusing a toast had no way to dismiss it, and the timer was not paused on focus
— so the toast could vanish while being read. This PR brings full keyboard parity with the
existing mouse behaviour.

Changes

components/ToastProvider.jsx

• tabIndex={0} on each toast card — makes cards reachable via Tab without requiring the user to
  navigate to the Close button first.
• onFocus → pause timer — mirrors the existing onMouseEnter pause. Records the
  previously-focused element so focus can be restored after dismissal.
• onBlur → resume timer — mirrors the existing onMouseLeave resume. Only resumes when focus
  leaves the entire toast region; moving focus between the card and its Close button keeps the
  timer paused.
• onKeyDown Escape → dismiss — pressing Escape on a focused toast (or its Close button)
  dismisses that toast only.
• Focus return — after any dismissal (Escape or Close button click), focus is restored to the
  element that was active before the user tabbed into the toast, preventing focus loss to .

components/ToastProvider.keyboard.test.tsx (new — 14 tests)

┌─────┬──────────┐
│ # │ Scenario │
├─────┼────────────────────────────┤
│ 1 │ tabIndex=0 present on card │
├─────┼─────────────────────────────────┤
│ 2 │ Focus pauses auto-dismiss timer │
├─────┼──────────────────────────────────────┤
│ 3 │ Blur outside container resumes timer │
├─────┼─────────────────────────────────────────────────────┤
│ 4 │ Focus moving card ↔ Close button keeps timer paused │
├─────┼─────────────────────────────────────────────────────┤
│ 5 │ Escape on card dismisses it │
├─────┼─────────────────────────────────────────────────────┤
│ 6 │ Escape on Close button dismisses it │
├─────┼─────────────────────────────────────────────────────┤
│ 7 │ Focus returns to pre-toast element after Escape │
├─────┼──────────────────────────────────────────────────────┤
│ 8 │ Focus returns to pre-toast element after Close click │
├─────┼──────────────────────────────────────────────────────┤
│ 9 │ No jest-axe violations when toast is focused │
├─────┼──────────────────────────────────────────────────────┤
│ 10 │ Escape only dismisses the focused toast, not all │
├─────┼──────────────────────────────────────────────────────┤
│ 11 │ Non-Escape keys (Enter, Space, Tab) do not dismiss │
├─────┼──────────────────────────────────────────────────────┤
│ 12 │ Escape-dismiss cancels the stale timer │
├─────┼──────────────────────────────────────────────────────┤
│ 13 │ Hover pause and focus pause coexist correctly │
├─────┼──────────────────────────────────────────────────────┤
│ 14 │ Card is reachable via userEvent Tab traversal │
└─────┴──────────────────────────────────────────────────────┘

README.md

Added a Toast notification keyboard behaviour table under the Accessibility section.

What was tested

• All 24 ToastProvider tests pass (14 new keyboard + 7 original + 3 dedupe).
• Existing ToastProvider.test.tsx and ToastProvider.dedupe.test.tsx pass unchanged.
• No jest-axe violations.
• Pre-existing build/lint failures (UploadZone.jsx duplicate name, missing eslint-plugin-react)
  are unrelated to this PR.

Accessibility contract

• role="status" / aria-live="polite" region is unchanged.
• All variant styling is unchanged.
• Focus-visible ring on the Close button is unchanged (focus-visible:ring-2
  focus-visible:ring-cyan-400).
  close Give the toast close button reliable Escape-to-dismiss and focus handling #151

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[edrizxabdulganiyu-blip]

can you please drop point