feat: add the Toast primitive

[ivanbanov]

Summary

Adds the Toast primitive as two packages:

• @dunky.dev/toast — the framework-free core: state machine, connect, and the behavior contract.
• @dunky.dev/react-toast — the thin React binding (compound components over the core machine).

A declarative, Radix-style toast — one component per toast, not an imperative toaster store. Each toast owns its open/close state (controlled and uncontrolled), announces as a status live region, auto-dismisses after its duration (Infinity = persistent), and pauses every timer while the viewport is hovered or focused. Resuming restarts the full duration — a documented deviation from Radix that keeps the timer contract inside the state machine.

Anatomy

<Toast.Provider label='Notifications' duration={5000}>
  <Toast.Viewport>
    <Toast>
      <Toast.Root>
        <Toast.Title />
        <Toast.Description />
        <Toast.Action />
        <Toast.Close />
      </Toast.Root>
    </Toast>
  </Toast.Viewport>
</Toast.Provider>

Behavior

• Root is role="status" with politeness driven by the toast type: foreground -> aria-live="assertive", background -> aria-live="polite"; aria-atomic announces the whole toast on update.
• Showing a toast never steals focus — its controls sit in the normal tab order through the viewport (role="region" landmark labelled by the provider's label, toasts as a list inside it).
• Hover or focus on the viewport pauses every toast's timer; leaving/blurring resumes with the full duration.
• Dismissing the toast that holds keyboard focus parks focus on the viewport (tabindex="-1"), so the user keeps their place and the focus-derived pause stays truthful.
• Root is labelled by the rendered Title and described by the rendered Description — an omitted part never leaves a dangling ARIA reference.
• Action and Close dismiss from inside; every open/close intent (including auto-dismiss) is reported through onOpenChange.

Test plan

• pnpm test:ci — 119 tests, 9 files, all passing
• pnpm typecheck
• pnpm lint
• pnpm format:check
• pnpm build

🤖 Generated with Claude Code