The not-authed flow told the user to paste their ngrok authtoken into the
chat so the agent could run `ngrok config add-authtoken` — putting a live
credential in the transcript, tool-call argv, and anything the transcript
syncs to. The user now runs the auth command in their own terminal; the
agent only verifies via `ngrok config check`, and a pasted token triggers a
rotate-and-reauth instruction. A static test pins that no agent-run bash
fence ever contains add-authtoken again.
Fixes#2335.
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>