Toast (Sonner) displayoverlay

Use Toast.Root from @repo/ploss/toast with bind:open to compose notification content through children. Toast.Title and Toast.Description provide semantic parts; the children snippet receives a close function for custom actions. A mounted Sonner.Toaster handles positioning, stacking and timers. Existing imperative notifications and promises remain available through Sonner.toast.

Ephemeral notification overlay. Supports promise, action, dismiss, and stacked positioning via Sonner.