feat(ui): render the CCTV camera picker from the store

The picker's options are data: CctvControls computes the cameras in view
and the closing note for those left out, keeps a focused picker's list and
prepends a camera activated under it, and publishes the options, disabled
state and selection. CctvPicker renders them keyed by camera id and
applies the selection once the options are in place; it updates only when
the controls publish, as the old picker did on layer notifications. A
picker about to be disabled no longer counts as focused.

This completes the CCTV panel: everything it shows is rendered from the
gev-cctv store.

src/ui/cctvBindings.js

@@ -61,7 +61,7 @@ export function _initCctvPanel() {
 
   // The picker defers rebuilds while focused; catch up once it lets go.
   this.listen(this._cctvSelect, 'blur', () => {
-    this._cctvSelectSource = null;
+    this._picker = null;
     this._renderCctvState(this._cctvState);
   });