feat(cli): add OpenUI Cloud LangGraph and Vercel AI SDK backends

[AbhinRustagi]

What

Adds the LangGraph and Vercel AI SDK backend overlays for the Cloud template. In both, the framework owns orchestration and application tools while OpenUI Cloud stays the Responses model provider and conversation store — reports, presentations, web search, image search and MCP remain provider-executed.

Changes

• LangGraph — src/agent/agent.ts builds the agent with createAgent() plus a middleware that points the model at Cloud, forwards only the newest message (Cloud holds the history), and strips Cloud-owned tool calls from graph state so ToolNode runs only app tools.
• Vercel AI SDK — a streamText() route with middleware that marks Cloud-executed tools as provider-executed, so the SDK streams them without dispatching them locally, plus a UI-chunk transform that makes completed Cloud tools display-only in the browser.
• Each overlay ships its own cloud-chat.tsx wired to the transport its route speaks — agUIAdapter() for LangGraph, vercelAIAdapter() + vercelAIMessageFormat for the AI SDK. The base template is untouched, so there's no transport map or backend prop to keep in sync as backends are added.
• Ignore .langgraph_api, written by the local Agent Server.

Pure additions — this PR modifies no existing template file.

Test Plan

• Verified locally

Built the CLI and scaffolded all three Cloud variants. Each gets the right adapter in its generated cloud-chat.tsx — agUIAdapter, vercelAIAdapter, and openAIResponsesAdapter for default — with no backend prop and no transport map anywhere. Also confirmed src/lib/tool-loop.ts is removed via files.remove and backends/ doesn't leak.

Checklist

• I updated docs/README when needed (see docs(cli): document backend framework selection #965)
• I considered backwards compatibility

[vercel]

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Project	Deployment	Actions	Updated (UTC)
openui-docs	Ready	Preview	Aug 24, 2026 9:00am