fix(street-level): own the framing flight and the nearest-photo lookup

From the IC8 review of #768, each with tests that fail before:

- P1: closing a photo, switching the layer off or destroying it stops the
  1.6 s framing flight toward that photo. The flight is claimed with a
  token before flyToBoundingSphere and released by its complete/cancel
  callbacks, so cancelFraming() calls camera.cancelFlight() only while
  the flight is still Street Level's: a newer navigation flight (a search
  result, a scene) is never cancelled. Turning FOLLOW on also stops it, so
  the tween cannot overwrite the follow view.
- P2: an older nearest-photo lookup can no longer replace a newer choice.
  The core owns one AbortController per lookup, aborted by a newer lookup,
  a direct open or cone click, closing the viewer, disable and destroy;
  the signal reaches source.nearestImages through the provider, and an
  aborted lookup never surfaces as an error.

Co-Authored-By: Claude Opus 5.5 <[email protected]>

src/layers/streetLevel/providers/mapillary/index.js

@@ -180,14 +180,15 @@ export function createMapillaryProvider({ source }) {
           loading: state.sequence.loading,
         }),
 
-        /** Nearest image that passes the imagery filter, or null. */
-        async nearestImage({ lat, lon }) {
-          const images = await source.nearestImages({
-            lat,
-            lon,
-            radius: NEAREST_RADIUS_M,
-            limit: NEAREST_LIMIT,
-          });
+        /**
+         * Nearest image that passes the imagery filter, or null. The core
+         * aborts `signal` once a newer request overtakes the lookup.
+         */
+        async nearestImage({ lat, lon }, { signal } = {}) {
+          const images = await source.nearestImages(
+            { lat, lon, radius: NEAREST_RADIUS_M, limit: NEAREST_LIMIT },
+            { signal },
+          );
           // The API returns the images in the radius in no particular order.
           const metres = (record) => {
             const [lon2, lat2] = (record.computed_geometry || record.geometry)