refactor(street-level): rename the Mapillary layer to street-level

Pure move: the layer id, panel id, CSS prefix, classes, exports and config
paths become provider-neutral (street-level, #street-level-panel, sl-);
the Mapillary-specific modules move under providers/mapillary/. Behaviour
is unchanged. The two sprite collections now register under distinct ids
instead of overwriting each other under 'mapillary'.

Co-Authored-By: Claude Fable 5.1 <[email protected]>

src/ui/panelChrome.js

@@ -14,7 +14,7 @@ const SHARE_PANEL_STATE_SPECS = Object.freeze([
   { id: 'cctv-panel' },
   { id: 'weather-panel' },
   { id: 'recent-imagery-panel' },
-  { id: 'mapillary-panel' },
+  { id: 'street-level-panel' },
   { id: 'radio-panel' },
   { id: 'scene-panel' },
   { id: 'global-context-panel' },
@@ -27,7 +27,7 @@ const COCKPIT_ENTRY_COLLAPSE_PANEL_IDS = Object.freeze([
   'cctv-panel',
   'weather-panel',
   'recent-imagery-panel',
-  'mapillary-panel',
+  'street-level-panel',
   'scene-panel',
   'pp-toggles',
   'global-context-panel',
@@ -290,7 +290,7 @@ export class PanelChrome {
       'cctv-panel',
       'weather-panel',
       'recent-imagery-panel',
-      'mapillary-panel',
+      'street-level-panel',
       'global-context-panel',
     ].includes(panelEl?.id);
     const collapsed = panelEl.classList.contains('collapsed');