Author a crit story with `crit story`

This skill authors a story-mode overview, then enters the same interactive review cycle as /crit (wait → address comments → next round). Invoke it only when the user explicitly asks for story generation; do not infer it from generic review, PR, or diff-review requests.

Primary path: author in-session with --guide / --prep / --story-file (do not run bare crit story, which spends agent_cmd tokens), then run bare crit to listen for Finish Review.