feat: add optional close button for toast dismissal

[lubauss]

Summary

Add a closeButton prop to <Toaster> that renders an X dismiss button on each toast, visible on hover. This provides an alternative to swipe-to-dismiss for desktop users.

Problem

Currently the only way to dismiss a toast (besides waiting for auto-dismiss) is swiping. Desktop users expect a close button, especially for sticky toasts (duration: null) that don't auto-dismiss.

Solution

New closeButton prop

<Toaster closeButton />

When enabled, each toast renders an X button (using the existing X icon) in the top-right corner. The button:

• Is hidden by default, fades in on toast hover
• Calls onDismiss() on click
• Is fully accessible: role="button", tabIndex, aria-label, keyboard support (Enter/Space)
• Does not interfere with swipe-to-dismiss

CSS

[data-sileo-close] {
  position: absolute;
  top: 0; right: 0; z-index: 30;
  opacity: 0;
  transition: opacity 150ms ease;
}
[data-sileo-toast]:hover [data-sileo-close] { opacity: 1; }

Files Changed

File	Changes
src/toast.tsx	Add closeButton prop to SileoToasterProps, pass to <Sileo>
src/sileo.tsx	Accept closeButton prop, render X button with a11y attributes
src/styles.css	Add [data-sileo-close] styles with hover reveal

Backward Compatibility

• closeButton defaults to false — no visual change unless opted in
• Swipe-to-dismiss still works alongside the button

Testing

1. <Toaster closeButton /> — hover over a toast, X button should fade in
2. Click X — toast should dismiss
3. Tab to button, press Enter — should dismiss
4. Verify swipe-to-dismiss still works
5. Without closeButton prop — verify no X button appears