Project Milestone

Use this skill only when explicitly invoked as $project-milestone. It owns Gate
3 planning and milestone revision, but never closes Gate 3; $project handles
closure when all milestones are complete.

Core Rules

• Read progress.txt fresh from disk before acting.
• Require Gate 2 [x] approval. If missing, tell the user to run
  $project-design.
• Produce the milestone README/status files, present them for review, and record
  approval only after checklist items are [x] or [-] with a reason.
• When both state files change, write milestone-status.txt first and
  progress.txt second.
• Ask concise chat questions for user choices; use structured input tools when
  available.
• Do not invoke the next skill automatically. Recommend the next explicit skill.
• Read the referenced workflow files before executing their corresponding steps;
  they contain required edge-case handling, review criteria, and artifact formats.

Workflow

1. Detect first invocation, subsequent invocation, revision mode, or all
   milestones-defined state from prd.md, progress.txt, and milestones/.
2. Read references/gate-3-milestone.md.
3. On first invocation, propose the full milestone sequence and write the
   approved sequence into the PRD Milestones section.
4. Define one milestone using assets/milestone-readme-template.md, creating:
   milestones/<NN>-<name>/README.md,
   milestones/<NN>-<name>/milestone-status.txt, and a Gate 3 review file.
5. In revision mode, read references/revision-mode.md, preserve completed
   features, and update affected milestone artifacts.
6. Update progress.txt with Gate 3 [~] In progress and the milestone summary
   line, using references/progress-format.md.

Reference Files

• references/gate-3-milestone.md
• references/revision-mode.md
• references/progress-format.md
• references/review-checklist-template.md
• assets/milestone-readme-template.md

Completion

Report created/updated artifacts and recommend $project-plan-feature for the
next unplanned feature or $project for status.