Remove login commands and magic link sends

[sergei1152]

Simplify login methods so agents dont get confused which one to pick. I also added a --json option to the login command to try and encourage claude to use its monitors functionality.

uv run parallel-cli login --json                                                                                                                                   nix-shell-env
{"event": "auth_start"}
{"event": "device_code", "verification_uri": "http://localhost:3000/getServiceKeys/device", "verification_uri_complete": "http://localhost:3000/getServiceKeys/device?user_code=CHQX-NQKP&onboard_variant=agent", "user_code": "CHQX-NQKP", "expires_in": 600, "browser_open_attempted": true, "browser_opened": true}
{"event": "auth_waiting"}
{"event": "auth_success"}