Adds guidance to prefer vertical slices (user-visible value) over
horizontal slices (technical layers) when planning and writing issues.
roadmap-planning skill:
- New "Vertical vs Horizontal Slices" section
- Demo test: "Can a user demo/test this independently?"
- Good vs bad examples table
- When horizontal slices are acceptable
issue-writing skill:
- New "Vertical Slices" section
- Demo test guidance
- Good vs bad issue titles table
- User-focused issue framing examples
Closes#31
Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>
