feat(display): answer the Display controls through the store with UiSegmented

The Display panel, the dock's style buttons and the clean-view exit call
the display store's actions, and DisplayBindings connects their handlers
to it, replacing the bindDisplayControls listeners. The detection
allocation and 3D model coverage choices render through a new kit
UiSegmented, which takes v-model, options, label,
stacked and disabled, and adds a keyboard policy, item classes and
per-option attributes.

Shell element fields and facade accessors that only the old listeners
read are removed. The package boundaries now own UiSegmented and the
UiPanel kit files, and the format scope drops the deleted test.

src/ui/kit/UiSegmented.vue

@@ -0,0 +1,118 @@
+<script setup>
+import { computed, nextTick } from 'vue';
+
+// Core's segmented control, with @halfpixel/ui-vue UiSegmented's
+// v-model, options, label, stacked and disabled so the two kits can merge.
+// Core adds `keyboard`, because its groups keep their own policy: `none`
+// (Tab reaches every option and arrows do nothing), `arrows` (a roving tab
+// stop that arrows move, as in ui-vue) or `radio` (arrows plus Home and
+// End). Each option may carry `attrs` (an id, data attributes, a tip), and
+// Core's classes sit beside the kit's: `gev-segmented`, `gev-segment` and the
+// selected option's `activeClass`. Not mirrored yet: an option's icon.
+const props = defineProps({
+  modelValue: { type: String, default: undefined },
+  /** `{value, label, icon?, disabled?, attrs?}`, labels already translated. */
+  options: { type: Array, required: true },
+  /** The group's accessible name, already translated. */
+  label: { type: String, required: true },
+  stacked: { type: Boolean, default: false },
+  /** The whole group is off: no option is in the tab order or answers. */
+  disabled: { type: Boolean, default: false },
+  keyboard: {
+    type: String,
+    default: 'arrows',
+    validator: (value) => ['none', 'arrows', 'radio'].includes(value),
+  },
+  /** Core's class on every option, beside `gev-segment`. */
+  itemClass: { type: String, default: undefined },
+  /** Core's class on the selected option. */
+  activeClass: { type: String, default: 'active' },
+});
+const emit = defineEmits(['update:modelValue']);
+// The option buttons, by index, for focus; not reactive state.
+const items = [];
+
+const selectedIndex = computed(() =>
+  props.options.findIndex((option) => option.value === props.modelValue),
+);
+const optionOff = (option) => props.disabled || !!option.disabled;
+/** The roving tab stop; with no selection, the first option. */
+const tabStop = computed(() =>
+  props.disabled ? -1 : Math.max(0, selectedIndex.value),
+);
+function tabindex(index) {
+  if (props.keyboard === 'none') return undefined;
+  return index === tabStop.value ? 0 : -1;
+}
+
+function choose(index) {
+  const option = props.options[index];
+  if (!option || optionOff(option)) return;
+  emit('update:modelValue', option.value);
+}
+/** Select the option `delta` away, wrapping past disabled ones, or `to` an end. */
+function move({ delta = 0, to = null }) {
+  const count = props.options.length;
+  if (!count || props.disabled) return;
+  const enabled = props.options
+    .map((option, index) => (option.disabled ? -1 : index))
+    .filter((index) => index >= 0);
+  if (!enabled.length) return;
+  let target;
+  if (to === 'first') target = enabled[0];
+  else if (to === 'last') target = enabled.at(-1);
+  else {
+    target =
+      selectedIndex.value < 0 ? (delta > 0 ? -1 : count) : selectedIndex.value;
+    do target = (((target + delta) % count) + count) % count;
+    while (props.options[target].disabled);
+  }
+  choose(target);
+  // Focus follows the selection once the options re-render.
+  nextTick(() => items[target]?.focus());
+}
+const STEPS = { ArrowRight: 1, ArrowDown: 1, ArrowLeft: -1, ArrowUp: -1 };
+function onKey(event) {
+  if (props.keyboard === 'none') return;
+  if (STEPS[event.key]) move({ delta: STEPS[event.key] });
+  else if (props.keyboard === 'radio' && event.key === 'Home')
+    move({ to: 'first' });
+  else if (props.keyboard === 'radio' && event.key === 'End')
+    move({ to: 'last' });
+  else return;
+  event.preventDefault();
+}
+</script>
+
+<template>
+  <div
+    role="radiogroup"
+    class="ui-segmented gev-segmented"
+    :class="{ 'ui-segmented--stacked': props.stacked }"
+    :aria-label="props.label"
+    :aria-disabled="props.disabled ? 'true' : undefined"
+    @keydown="onKey"
+  >
+    <button
+      v-for="(option, index) in props.options"
+      :key="option.value"
+      v-bind="option.attrs"
+      :ref="(el) => (items[index] = el)"
+      type="button"
+      role="radio"
+      class="ui-segmented__item ui-focus gev-segment"
+      :class="[
+        props.itemClass,
+        {
+          'ui-segmented__item--on': option.value === props.modelValue,
+          [props.activeClass]: option.value === props.modelValue,
+        },
+      ]"
+      :aria-checked="String(option.value === props.modelValue)"
+      :disabled="optionOff(option)"
+      :tabindex="tabindex(index)"
+      @click="choose(index)"
+      >{{ option.label }}</button
+    >
+  </div>
+</template>