feat(Select): add label prop to SelectActivator

[sridhar-3009]

SelectActivator is a combobox trigger but had no way to carry an accessible label when the visible label is in a sibling element, and no typeahead for keyboard users. This closes both gaps.

Changes

packages/0/src/components/Select/SelectActivator.vue

• New optional label prop → emitted as aria-label on the activator (passed through to SelectActivatorProps / SelectActivatorSlotProps.attrs)
• In onKeydown, when the listbox is open and a printable character key is pressed (single char, no Ctrl/Meta/Alt modifier), delegates to context.virtualFocus.typeahead(e.key) — jumps virtual focus to the first non-disabled item whose text content starts with that character

packages/0/src/composables/useVirtualFocus/index.ts

• New typeahead(char: string) => void method on VirtualFocusReturn (interface + implementation)
• Searches all non-disabled items starting from the position after the currently highlighted one (wrapping around), finds the first whose visible text starts with the typed char (case-insensitive), and calls highlight() on it

WCAG coverage

• 2.1.1 Keyboard — printable-char typeahead is required for listboxes per ARIA authoring practice (APG Listbox pattern §6.5)
• 4.1.2 Name, Role, Value — aria-label on the combobox satisfies the accessible name requirement when the label element is not associated via <label for>

Refs #613 (already closed by #633; this PR completes the Select half of the same audit).

[github-actions]

✅ Changeset found — this change will be included in the next release. Thanks!

[johnleider]

This PR has been split. The printable-char typeahead was removed in 9ab7835 and now lives as a design item in #908: the typeahead name breaks VirtualFocusReturn's imperative verb family, its placement is contested (useVirtualFocus vs a shared text-matching seam that useRovingFocus could also consume), and the implementation was partial APG — no timed multi-character buffer, and inert while the listbox is closed where native <select> responds. The PR now carries only the SelectActivator label prop, which resolves the accessible-name gap on its own and is mergeable standalone. The typeahead prototype remains fully recoverable at the pre-split head, bdb78da. Thanks for the contribution — the typeahead work isn't lost, it just needs the design pass before freezing onto the composable API.