Lazy-load mediabunny on web (#11094)

Co-authored-by: Claude Fable 5 <noreply@anthropic.com>

src/lib/media/video/mediabunny.ts

@@ -0,0 +1,20 @@
+type MediaBunnyModule = typeof import('mediabunny')
+
+let promise: Promise<MediaBunnyModule> | undefined
+
+/**
+ * Lazily loads mediabunny into its own webpack chunk and caches the resulting
+ * promise so the module is fetched at most once. If the import fails (e.g. a
+ * transient chunk-load error), the cached promise is reset so a later call can
+ * retry the load.
+ */
+export function loadMediaBunny(): Promise<MediaBunnyModule> {
+  promise ??= import(/* webpackChunkName: "mediabunny" */ 'mediabunny').catch(
+    e => {
+      // reset so a later attempt can retry after a transient chunk-load failure
+      promise = undefined
+      throw e
+    },
+  )
+  return promise
+}