perf(webui): lazily load module descriptors

docs/MODULE_ARCHITECTURE.md

@@ -624,11 +624,18 @@ Uninstall remains non-destructive unless the operator explicitly requests
 
 ## WebUI Contract
 
-A WebUI module exports a `PlatformWebModule` from its package. The object contributes local/fallback metadata and route render functions.
+A WebUI module exports a `PlatformWebModule` from its package. The object
+contributes local/fallback metadata and route render functions. The package
+must ship `src/module.ts` with the default contribution export: Core's Vite
+host imports that descriptor directly after the backend reports the module as
+enabled. This keeps package-root re-exports from pulling page implementations
+into the initial shell.
 
 Example:
 
 ```ts
+const FilesPage = lazy(() => import("./features/files/FilesPage"));
+
 export const filesModule: PlatformWebModule = {
   id: "files",
   label: "Files",
@@ -643,6 +650,11 @@ export const filesModule: PlatformWebModule = {
 };
 ```
 
+Route pages and substantial panels must use stable lazy imports. Core supplies
+the shared loading and retryable error state around route rendering. The
+initial static import closure and largest asynchronous chunk are enforced by
+the budgets documented in [WEBUI_BUNDLE_BUDGETS.md](WEBUI_BUNDLE_BUDGETS.md).
+
 WebUI modules receive only the core route context:
 
 - `settings`