feat(globe): answer the clear and share actions through the globe actions store

The top-center bar is now GlobeActions.vue. The shell publishes whether a
clear is under way and answers the clear and share buttons through the
globe actions store, instead of binding listeners and writing attributes on
the buttons. A shell disposed mid-clear resets the busy state, so the next
shell's bar is not left busy. bindClearLayersControl stays exported and is
deprecated.

src/ui/shellElements.js

@@ -63,10 +63,8 @@ export function readShellElements(document = globalThis.document) {
     _cctvSourceBadge: document.getElementById('cctv-source-badge'),
     _cctvMeta: document.getElementById('cctv-meta'),
     _cctvSummary: document.getElementById('cctv-summary'),
-    _shareBtn: document.getElementById('share-btn'),
     _tiltMapBtn: document.getElementById('tilt-map-view'),
     _northUpBtn: document.getElementById('north-up-view'),
-    _clearSelectedLayersBtn: document.getElementById('clear-selected-layers'),
     _resetGlobeBtn: document.getElementById('reset-globe-view'),
     _cockpitResetGlobeBtn: document.getElementById('cockpit-reset-globe'),
     _locationSearch: document.getElementById('location-search'),