feat: add infrastructure for MCP Apps (#10259)

* feat: add infrastructure for MCP Apps

### Description
Adds support for returning structured content from tools, which is used by MCP Apps to pass complex data to the host. Also updates the resource index.

### Scenarios Tested
- Verified build and file changes.

* fix: resolve build errors and address review comments on infra

### Description
- Removes imports and registry entries for UI resources that are not yet available in this branch (login, update_environment, deploy, init).
- Replaces as any in toContent with an intersection type for better type safety.

### Scenarios Tested
- Verified build succeeds.

Author: joehan

src/mcp/util.ts

@@ -41,7 +41,8 @@ export function toContent(
   const suffix = options?.contentSuffix || "";
   return {
     content: [{ type: "text", text: `${prefix}${text}${suffix}` }],
-  };
+    structuredContent: data,
+  } as CallToolResult & { structuredContent: any };
 }
 
 /**