harness-plan — Epic Planning for the Harness Control Loop

Fills the gap between harness-init (environment setup) and harness-loop (autonomous sprints). Runs once per epic. Re-runs continue the same epic draft from wherever it was interrupted.

The skill orchestrates the Planner sub-agent through three artifacts:

1. product-spec.md — What / Why / Out of Scope / Constraints (interactive)
2. roadmap.md — sprint decomposition with bundling: split|bundled
3. One tracker Issue per sprint (when _config.yml.tracker != none)

After this skill finishes, the project is ready for /harness-loop.

Required Reading — Open BEFORE doing the step