feat(ui): render the Cockpit utility launchers and compact Radio controls from a store

The Display and Radio launchers, their popovers and the compact Radio
transport, Enable button and volume now render from the Radio store.
RadioControls owns the disclosure state; Cockpit Escape and the Display
reveal read that state instead of the DOM, and the Enable toggle guards
re-presses synchronously. The compact transport reuses the panel's
transport state and adds only its glyph and title.

src/ui/shellElements.js

@@ -46,16 +46,11 @@ export function readShellElements(document = globalThis.document) {
     ),
     _cockpitDisplayPanel: document.getElementById('cockpit-display-panel'),
     _cockpitRadioToggleBtn: document.getElementById('cockpit-radio-toggle-btn'),
-    _cockpitRadioPanel: document.getElementById('cockpit-radio-panel'),
     _cockpitRadioEnableBtn: document.getElementById('cockpit-radio-enable-btn'),
-    _cockpitRadioStation: document.getElementById('cockpit-radio-station'),
     _cockpitRadioPrevBtn: document.getElementById('cockpit-radio-prev-btn'),
     _cockpitRadioPlayBtn: document.getElementById('cockpit-radio-play-btn'),
     _cockpitRadioNextBtn: document.getElementById('cockpit-radio-next-btn'),
     _cockpitRadioVolume: document.getElementById('cockpit-radio-volume'),
-    _cockpitRadioVolumeValue: document.getElementById(
-      'cockpit-radio-volume-value',
-    ),
     _radioLayerState: document.getElementById('radio-layer-state'),
     _radioEnableBtn: document.getElementById('radio-enable-btn'),
     _radioFilter: document.getElementById('radio-filter'),