Pause Toast auto-dismiss timer on hover

[barney-w]

Toasts auto-dismiss after 5 seconds, but the countdown keeps running even when you're hovering over the toast — so it can vanish while you're reading it.

What needs doing:

• Clear the dismiss timeout on mouseenter
• Restart it (with remaining time) on mouseleave
• Add tests covering the pause/resume behaviour

Where to look:

• Component: packages/core/src/feedback/Toast/Toast.tsx
• Tests: packages/core/src/feedback/Toast/__tests__/Toast.test.tsx