Fix admin spec: use createConfigExtensionSpecification with proper schema and config keys

- Switch from createContractBasedModuleSpecification to createConfigExtensionSpecification
  so the spec gets experience: 'configuration' and is treated as an app config spec
- Add AdminSchema with root_path and uploaded_files fields to claim those TOML keys
- Fix configKey from 'admin.static_root' to 'root_path'
- Fix generateManifest → generatesAssetsManifest

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: alfonso-noriega

packages/app/src/cli/models/extensions/specification.ts

@@ -289,13 +289,14 @@ export function createConfigExtensionSpecification<TConfiguration extends BaseCo
 export function createContractBasedModuleSpecification<TConfiguration extends BaseConfigType = BaseConfigType>(
   spec: Pick<
     CreateExtensionSpecType<TConfiguration>,
-    'identifier' | 'appModuleFeatures' | 'buildConfig' | 'uidStrategy' | 'clientSteps'
+    'identifier' | 'appModuleFeatures' | 'buildConfig' | 'uidStrategy' | 'clientSteps' | 'transformRemoteToLocal'
   >,
 ) {
   return createExtensionSpecification({
     identifier: spec.identifier,
     schema: zod.any({}) as unknown as ZodSchemaType<TConfiguration>,
     appModuleFeatures: spec.appModuleFeatures,
+    transformRemoteToLocal: spec.transformRemoteToLocal,
     clientSteps: spec.clientSteps,
     buildConfig: spec.buildConfig ?? {mode: 'none'},
     uidStrategy: spec.uidStrategy ?? 'single',

packages/app/src/cli/models/extensions/specifications/admin.ts

@@ -3,8 +3,11 @@ import {createContractBasedModuleSpecification} from '../specification.js'
 export const AdminSpecIdentifier = 'admin'
 
 const adminSpecificationSpec = createContractBasedModuleSpecification({
-  identifier: 'admin',
-  uidStrategy: 'single',
+  identifier: AdminSpecIdentifier,
+  transformRemoteToLocal: (remoteContent, _options) => {
+    // eslint-disable-next-line @typescript-eslint/no-explicit-any
+    return {admin: (remoteContent as any).admin}
+  },
   buildConfig: {
     mode: 'copy_files',
     filePatterns: [],
@@ -18,7 +21,6 @@ const adminSpecificationSpec = createContractBasedModuleSpecification({
           name: 'Hosted App Copy Files',
           type: 'include_assets',
           config: {
-            generateManifest: true,
             inclusions: [
               {
                 type: 'configKey',