feat(core): add readiness adapters for map and visualization libraries (#1548)

Add readiness-only runtime adapters for Mapbox GL JS, Leaflet, Google
Maps, MapLibre GL JS, and D3. Each adapter gates `__renderReady` until
the library's async initialization completes, preventing the renderer
from capturing blank or half-loaded frames.

Built on the `getReadyPromise` adapter contract from #1543. A shared
`createReadinessAdapter()` helper in `_readiness.ts` owns the
settled-tracking WeakSet, promise-identity stability, and
`Promise.allSettled` gate — each adapter provides only its type, window
global name, and `waitFor` callback.

Readiness signals per library:
- Mapbox / MapLibre: `map.loaded()` + `map.on('load', ...)`
- Leaflet: `map.whenReady(cb)`
- Google Maps: `map.addListener('tilesloaded', cb)` with handle cleanup
- D3: `transition.end()` promise

50 unit tests across 5 test files covering happy path, no-instances,
stable promise identity, post-settle drain, loaded-before-subscribe
race, and listener cleanup. 5 producer regression tests with
Docker-generated baselines for end-to-end render verification.

packages/core/src/runtime/init.ts

@@ -6,6 +6,11 @@ import { createGsapAdapter } from "./adapters/gsap";
 import { createAnimeJsAdapter } from "./adapters/animejs";
 import { createLottieAdapter } from "./adapters/lottie";
 import { createThreeAdapter } from "./adapters/three";
+import { createMapboxAdapter } from "./adapters/mapbox";
+import { createLeafletAdapter } from "./adapters/leaflet";
+import { createGoogleMapsAdapter } from "./adapters/google-maps";
+import { createMaplibreAdapter } from "./adapters/maplibre";
+import { createD3Adapter } from "./adapters/d3";
 import { createTypegpuAdapter } from "./adapters/typegpu";
 import {
   patchVideoTextureCompat,
@@ -1913,6 +1918,11 @@ export function initSandboxRuntimeModular(): void {
     createAnimeJsAdapter(),
     createLottieAdapter(),
     createThreeAdapter(),
+    createMapboxAdapter(),
+    createLeafletAdapter(),
+    createGoogleMapsAdapter(),
+    createMaplibreAdapter(),
+    createD3Adapter(),
     createTypegpuAdapter(),
     createGsapAdapter({ getTimeline: () => state.capturedTimeline }),
   ] as RuntimeDeterministicAdapter[];