Prd Implementation Precheck

This hooks into Claude when you say "implement the PRD" and forces a preflight review before any code gets written. It reads your spec, checks for scope creep, missing edge cases (null handling, error states, concurrent edits), and whether your proposal conflicts with existing patterns in the codebase. The precheck report calls out blockers versus warnings, then explicitly asks if you want to proceed or revise. It's opinionated about stopping you from building the wrong thing, which is either going to save you hours of rework or feel like unnecessary friction depending on how well you write specs. The edge case checklist is thorough enough that you'll probably discover gaps you didn't think about.