fix(VOverlay): always return focus to activator on Escape key

[mixelburg]

Fixes #22560

Problem

Keyboard focus was lost after closing a v-menu (or any overlay) with the Escape key in certain scenarios:

• Menu opened by clicking a button but focus was not yet captured inside the content (e.g. before the user tabbed in)
• Coordinate-based menus where the activator element is not keyboard-focusable

Root cause: The focus-return logic in VOverlay.onKeydown was gated behind a check that the active element was inside the overlay content at the time Escape was pressed:

// Before
if (contentEl.value?.contains(document.activeElement)) {
  activatorEl.value?.focus()
}

When focus was outside the content (e.g. still on the page body), the activator was never re-focused.

Fix

Remove the conditional so focus always returns to the activator when Escape closes an overlay:

// After
activatorEl.value?.focus()

If the activator is not focusable (e.g. a plain <div> used for coordinate-based menus), the focus() call is a silent no-op — same behaviour as before for those cases. For button-based activators this ensures focus is reliably returned.

Also adds a browser test covering this scenario.