Merge origin/main: keep the provider registry, slim it

main grew the Street Level provider registry while this branch removed it
(#982–#985: injected providers, an empty composition, the `r` switch field).
The registry, params, uiState and pick router come back as main has them and
the slimmed layer sits behind the provider contract:

- The core (index.js) drives providers as on main, without surface modes,
  ground casting, FOLLOW, prewarm and nearest-image lookups. A provider's key
  status is asked with a 10 s timeout and asked again on a switch-on while no
  key is known.
- Mapillary is mapillaryProvider.js over the slim coverage, sequences and
  viewer modules, which read the filter and the active flag from the provider
  context.
- The viewer host mounts one provider adapter at a time, no prewarm.
- The panel has a chip per provider again (the pill switches the layer);
  no legend, EXPAND stays the Fullscreen API.
- The contract drops what no provider implements: groundCaster, meshSampler,
  getSurface/setSurface, nearestImage, prewarm, reportError, the legend and
  surface fields of the UI snapshot.

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

package.json

@@ -162,6 +162,7 @@
     "./layers/vessels": "./src/layers/vessels/index.js",
     "./layers/earthquakes": "./src/layers/earthquakes/index.js",
     "./layers/recent-imagery": "./src/layers/recentImagery/index.js",
+    "./layers/recent-imagery/source": "./src/layers/recentImagery/source.js",
     "./layers/perimeters": "./src/layers/perimeters/index.js",
     "./sources/firms-csv": "./src/data/firmsCsv.js",
     "./layers/firms": "./src/layers/firms/index.js",
@@ -172,6 +173,7 @@
     "./layers/traffic": "./src/layers/traffic/index.js",
     "./layers/bikeshare": "./src/layers/bikeshare/index.js",
     "./layers/directions": "./src/layers/directions/index.js",
+    "./layers/directions/source": "./src/layers/directions/source.js",
     "./layers/cctv": "./src/layers/cctv/index.js",
     "./layers/alpr": "./src/layers/alpr/index.js",
     "./layers/radio": "./src/layers/radio/index.js",
@@ -260,6 +262,7 @@
       "node": "./server/providers/mapillary.js"
     },
     "./layers/street-level": "./src/layers/streetLevel/index.js",
+    "./layers/street-level/mapillary": "./src/layers/streetLevel/mapillaryProvider.js",
     "./layers/street-level/mapillary/source": "./src/layers/streetLevel/source.js",
     "./tools": "./src/tools/index.js",
     "./tools/mcp": "./src/tools/mcp/index.js",