Allow terminal attachment to phone-spawned Remote Control sessions

Feature Request

Problem: When using Remote Control in multi-session spawn mode (claude remote-control --spawn same-dir), sessions created from the phone/web cannot be resumed or attached to from a local terminal. claude --resume doesn't find them because they live inside the Remote Control server process, not as independent local sessions.

Current workaround: Use claude.ai/code in a browser to interact with phone-spawned sessions from the computer — but this loses the full terminal experience.

The asymmetry:

• Terminal → phone (single session /remote-control): works seamlessly
• Terminal → phone (multi-session --spawn): works, phone can spawn new sessions
• Phone → terminal (resume spawned session in CLI): not possible

Proposed solution: Something like claude --attach <cse_session_id> that connects a terminal to a running Remote Control session, giving full CLI access to sessions originally spawned from the phone or web.

Use case: Start sessions on your phone while away from your desk, then seamlessly pick them up in the terminal when you're back at your computer — the reverse of the existing flow.