gat-milestonelisted

# Milestone This skill writes: - `production/milestone.md` It does not create milestone directories, task lists, technical designs, prompt packs, or implementation files. Those belong to the downstream engineering workflow. ## Phase 1: Validate Inputs Fail if any of these are missing: - `design/gdd/game.md` - `design/gdd/systems-index.md` - `design/art/art-direction.md` Also stop if no system GDDs exist in `design/gdd/` besides `game.md` and `systems-index.md`. Read: - `design/gdd/game.md` - `design/gdd/systems-index.md` - all existing `design/gdd/*.md` except `game.md` and `systems-index.md` - all existing `design/content/*-data.md` - all existing `design/narrative/*.md` - `design/art/art-direction.md` - all existing `design/art/*-art.md` - `templates/plan/milestone.md` - `production/milestone.md` if exists ## Phase 2: Hand Off To The Planner Spawn `gat-planner` agent with all read content plus: - instruction to write or update `production/milestone.md` - instruction to split the project into ordered milestone handoff slices (`M01`, `M02`, ...) - instruction not to create milestone directories, task lists, technical designs, prompt packs, or code - planning focus from argument if provided The planner should: - choose a small set of meaningful milestones that can be handed off one stage at a time - give each milestone a clear goal, player-facing outcome, and named system set - define what is in scope and explicitly out of scope for each milestone - include desig