Enable MCP user verification in the TUI

[copyberry]

Enable MCP user verification in the TUI

Why

The TUI automatically canceled MCP user verification requests, preventing users from completing verification and approving them.

What changed

• Show verification prompts for active and inactive threads, with actions to verify and approve or cancel.
• Run approved verification through the local app-server's userVerification/verify RPC and return the proof to the original request. Cancel on failure and show a warning in the requesting thread; remote workspaces remain unsupported.
• Deduplicate prompts, preserve foreground streaming when another thread requests verification, and surface queued prompts when returning from a side conversation.
• Cancel verification when its thread is discarded and ignore stale results after cancellation.

Testing

Add RPC, routing, and snapshot tests covering successful verification, unsupported binaries and remote workspaces, cancellation and late proofs, prompt replay, side conversation switching, and foreground stream preservation.

[github-actions]

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