ax:narrate - write the session's story as a structured narration

You were there. This skill turns YOUR OWN memory of the session into a reviewable artifact: 3-7 stops in reading-flow order, each anchored to real evidence - code hunks, turn numbers, user quotes, failures. The point is to capture what a PR diff never shows: the corrections, the dead ends, the recoveries.

The artifact validates against SessionNarration in apps/studio/src/routes/narration-types.ts and renders in ax studio.