feat(kit): render the chips with UiChip and UiButton

UiChip is a non-interactive label chip and renders the voice
card's chips. The pressable chips and pills are pressed toggles, so the
rail card chips, map source chips and city and place pills render through
UiButton with pressedClass, keeping their classes, attributes and the
classes other code adds. The pills now report aria-pressed.

docs/VUE-MIGRATION.md

@@ -61,7 +61,10 @@ adapter is gone.
 `active`); its pressed classes toggle through `classList`, so a class other
 code adds (a voice highlight) survives a press. Every pressed toggle in the
 views is a `UiButton` except Bhote Koshi's cinematic button and the
-tilt-map button, whose owners still write their state into the DOM.
+tilt-map button, whose owners still write their state into the DOM. Core's
+pressable chips and pills (rail card chips, map sources, cities and places)
+are `UiButton`s too; `UiChip` is ui-vue's non-interactive label chip, used by
+the voice card.
 `UiSlider` keeps the native range input where ui-vue draws a
 `role="slider"` track, so Core's keyboard, form behaviour and styling stay;
 it takes ui-vue's `v-model`, `min`, `max`, `step` and `disabled`, emits a