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/app/layers/streetLevel.js

@@ -0,0 +1,19 @@
+import { createStreetLevelLayer } from '../../layers/streetLevel/index.js';
+import * as sprites from '../../data/spriteOrder.js';
+import * as picking from '../../data/pickRegistry.js';
+import * as input from '../../data/inputOwnership.js';
+import * as render from '../../renderGovernor.js';
+
+/** Construct the Street Level layer using the application scene owners and a supplied source. */
+export function createApplicationStreetLevel({ surface, source }) {
+  return createStreetLevelLayer({
+    source,
+    services: {
+      sprites,
+      picking,
+      input,
+      render,
+      ground: surface?.groundFloor ?? null,
+    },
+  });
+}