docs: redirect testing, drag-drop docs to adev (angular#31845)

Author: mmalerba

docs/src/app/routes.ts

@@ -9,6 +9,13 @@
 import {Routes} from '@angular/router';
 import {CanActivateComponentSidenav} from './pages/component-sidenav/component-sidenav-can-load-guard';
 
+function externalRedirect(target: string) {
+  return () => {
+    window.location.href = target;
+    return ''; // unused due to redirect above
+  };
+}
+
 export const MATERIAL_DOCS_ROUTES: Routes = [
   {
     path: '',
@@ -25,6 +32,31 @@ export const MATERIAL_DOCS_ROUTES: Routes = [
   // Since https://github.com/angular/components/pull/9574, the cdk-table guide became the overview
   // document for the cdk table. To avoid any dead / broken links, we redirect to the new location.
   {path: 'guide/cdk-table', redirectTo: '/cdk/table/overview'},
+  // Component harness, drag & drop docs have moved to angular.dev
+  {
+    path: 'cdk/testing',
+    redirectTo: externalRedirect('https://angular.dev/guide/testing/component-harnesses-overview'),
+  },
+  {
+    path: 'cdk/testing/api',
+    redirectTo: externalRedirect('https://angular.dev/api#angular_cdk_testing'),
+  },
+  {
+    path: 'cdk/testing/:tab',
+    redirectTo: externalRedirect('https://angular.dev/guide/testing/component-harnesses-overview'),
+  },
+  {
+    path: 'cdk/drag-drop',
+    redirectTo: externalRedirect('https://angular.dev/guide/drag-drop'),
+  },
+  {
+    path: 'cdk/drag-drop/api',
+    redirectTo: externalRedirect('https://angular.dev/api#angular_cdk_drag-drop'),
+  },
+  {
+    path: 'cdk/drag-drop/:tab',
+    redirectTo: externalRedirect('https://angular.dev/guide/drag-drop'),
+  },
   // In v19, the theming system became based on system variables and the mat.theme mixin.
   // The following guides were consolidated into the main theming guide, which redirects
   // users to v18 docs if they are looking for this content.

package.json

@@ -21,6 +21,7 @@
     "build-docs-content": "node --no-warnings=ExperimentalWarning --loader ts-node/esm/transpile-only ./scripts/build-docs-content-main.mts",
     "build-and-check-release-output": "node --no-warnings=ExperimentalWarning --loader ts-node/esm/transpile-only scripts/build-and-check-release-output.mts",
     "dev-app": "ibazel run //src/dev-app:devserver",
+    "docs-app": "ibazel run //docs:serve",
     "universal-app": "bazel run //src/universal-app:server",
     "test": "node ./scripts/run-component-tests.js",
     "test-local": "pnpm -s test --local",