feat: MCP-APPS support

MCP Apps allow MCP servers to expose rich, interactive UI workflows — including forms, multi-step views, actions, and app-like interfaces — directly inside an MCP-compatible client.

Adding support for MCP Apps would enable cloudflare-os to run structured, interactive “mini apps” provided by MCP servers, instead of relying exclusively on plain text-based tool interactions.

- interactive task flows
- buttons, forms, menus, lists, navigable views
- multi-step wizards and app-like interfaces
- stateful sessions and context

Supporting MCP Apps would dramatically improve the user experience and enable much richer workflows directly inside cloudflair-os.

## What implementation might include

- Recognizing the apps capability during the MCP handshake
- Rendering UI components defined by the Apps spec
- Handling user input, actions, and event callbacks
- Managing view navigation and app session state
- Passing context between user interactions and the MCP server
- (Optional but recommended) supporting the MCP-UI reference component library: https://mcpui.dev/

## Reference
Repo: https://github.com/modelcontextprotocol/ext-apps
Online test server: https://mcpplaygroundonline.com/mcp-test-client

Start by reading the MCP Apps specification in the linked ext-apps repository and compare its requirements with the existing MCP flow in cloudflare-os. Use the linked online test server to identify the handshake, rendering, interaction, navigation, and session behaviors that would need to work before considering the feature complete.

Written by the indexing model from the issue text.