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.

docs/VUE-MIGRATION.md

@@ -37,8 +37,8 @@ one-panel rule too. Share links continue to record which panels are open.
 ## Component kit
 
 `src/ui/kit/` holds the generic components: `UiRail`, `UiTooltip`, `UiIcon`,
-`UiButton` and `UiPanel` so far, with more (`UiSegmented`, `UiSelect` and
-so on) joining as the controls they serve are converted. One component
+`UiButton`, `UiPanel` and `UiSegmented` so far, with more (`UiSlider`,
+`UiSelect` and so on) joining as the controls they serve are converted. One component
 serves every use of a control, with props for the differences (`UiPanel`'s
 `sideways`, `glow`, `scroll`), rather than a copy per panel. Names, props,
 events and class names follow Halfpixel's `ui-vue` kit so the two can merge
@@ -50,6 +50,8 @@ its own classes beside it. They contain no application state.
 `collapsed` drives only the button and `ui-panel--collapsed`: the panel's
 owner hides the body by writing the root's `collapsed` class at once, and
 there is no `closable`, since Core's panels collapse rather than close.
+`UiSegmented` adds `keyboard` (`none`, `arrows` as in ui-vue, or `radio` with
+Home and End), since each of Core's groups keeps its own keyboard policy.
 
 Controls share one skin, so every panel reads the same. Every scrolling
 surface carries the kit's `.ui-scroll` (ui-vue's name), which draws the thin