Convert /review to skill

[ericelliott]

1. Keep everything as close to exactly the same as possible while adding the skill requirements.
2. Make sure reminders to use proper skills for the tech stack are included here.
3. Make sure there's a reference in AGENTS.md to ref to stack.

Stack should should be in aidd-custom/skills/stack/SKILL.md and fall back to ai/skills/stack/SKILL.md

Note: Skills thing should be implemented in #142