feat(controls): render every segmented group with UiSegmented

Street Level's fit and panorama filters and Recent Imagery's mode render
through the kit's UiSegmented, and their owners answer the choice
through the Street Level store (setPano, setRenderMode) and the
readout's onSetMode. The imperative segmentedControl.js adapter and its
test go. UiSegmented moves focus at once on a key, a radio group from
the option holding focus and an arrows group from the selection, and
asks for a change only when the key lands somewhere new.

docs/VUE-MIGRATION.md

@@ -51,7 +51,11 @@ its own classes beside it. They contain no application state.
 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.
+Home and End), since each of Core's groups keeps its own keyboard policy, and
+`itemClass`/`activeClass` for Core's segment classes. A key moves focus at
+once and asks for a change only when it lands on another option. Every
+segmented group in Core is a `UiSegmented`; the old `segmentedControl.js`
+adapter is gone.
 
 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