[FEATURE] Show QR code in terminal when starting remote-control session

When starting a remote-control session, the URL is printed as plain text. On a phone, this requires manual typing or a separate copy-paste workflow.

It would be convenient if Claude Code rendered a QR code directly in the terminal (UTF8 block characters) alongside the URL, so users can simply scan it with their phone camera.

This is a small quality-of-life improvement that removes friction from the remote-control flow — especially since the primary use case is connecting from a mobile device.