useLabelKeyboard now accepts labels as Label[] | (() => Label[]).
The keymap is rebuilt on every keypress from the getter result instead of
being captured once at construction time — so keys 1–9 now fire correctly
after the async /api/config/labels fetch completes.
LabelView passes () => labels.value so the reactive ref is read lazily.
New test: 'evaluates labels getter on each keypress' covers the async-load
scenario (empty list → no match; push a label → key fires).
