Development workflow with vendored Pocock skills

CLAUDE.md now anchors a 6-step workflow that runs from grilling an idea, writing a PRD, planning with personas, slicing into vertical issues, building in parallel, and archiving on merge. Eight skills are vendored at .claude/skills/: /grill-me, /grill-with-docs, /prototype, /to-prd, /to-issues, /tdd, /handoff, /improve-codebase-architecture. Hard rules cover token budgets, TDD timing, fresh-context review, vertical slicing, release discipline, and trust-surface invariants.