POST /api/sessions/:id/prompt claims a session's one naming attempt and runs
claude -p --model haiku in the background; the answer is reduced to a short
slug and replaces the generated handle, settling the session at Haiku. A
chosen name, a rename mid-run, a missing binary or a timeout all leave the
handle alone. The prompt goes to the child on stdin and is never logged.
Refs #131
Miguel Palhas
e7b323b412