[Feature] Select: accessible-name mechanism and printable-character typeahead

From the #543 WS4 audit. Two APG select-only-combobox gaps that need API additions (cheap ARIA fixes are landing separately):

1. No accessible name: SelectActivator.vue:118-129 renders role=combobox with no aria-label/aria-labelledby and no prop to supply one — child text is the value, not the name, so the control is unnamed. Add label/ariaLabelledby passthrough (~8 LOC).
2. No typeahead: SelectActivator.vue:74-114 handles arrows/Home/End/Enter/Space/Esc/Tab only; APG expects debounced printable-character type-to-jump (~20 LOC, needs a buffer).

Reference: Combobox implements both concerns correctly (ComboboxControl.vue:150-159).