Task: Spike: capture promotion runbook and compass support

Define the canonical capture→story promotion flow and determine how much of it compass capture promote should automate. Promoting a capture differs from starting a new story in three important ways:

• The capture's UUID must be inherited by the story (identity continuity — existing id-links stay valid).
• The story's Goal and Acceptance are populated from the capture's * What and * Why sections, not written from scratch.
• The capture file must be deleted (git rm) and its row removed from any index file (sprint capture.org, backlog bucket index).

Currently compass capture promote only prints instructions; it does not execute the steps. This spike decides whether to automate it, and in either case produces a runbook the LLM can follow.

• [ ] The three distinctions between promotion and new-story creation are documented (UUID inheritance, content population, capture cleanup).
• [ ] compass capture promote evaluated: current behaviour documented; gap between current and desired behaviour articulated.
• [ ] A promote_capture_to_story runbook written (or a decision made to automate in compass with a note on what the automation requires).
• [ ] Recommendation recorded in * Result: automate vs. manual runbook, with rationale and any follow-up tasks created.

(Transient implementation strategy. Written when work starts; distilled into the parent story's * Decisions and cleared when the task closes. Plans do not outlive their task.)