v0.4.0 - target repos stop receiving toolkit docs

Changed

• A target repo no longer receives the toolkit's own documentation. Skill
  README.md pages describe THIS repository, so shipping them put roughly
  1300 lines of irrelevant prose into every adopting repo's .claude/. They
  now stay canonical, alongside *.test.ts and eval.yaml. The one deliberate
  exception is hooks/README.md: hooks execute on the target's machine, so
  documenting what runs there is transparency rather than clutter.

Added

• Drift guards for the human documentation layer, which nothing watched before:
  every rule must have a docs/rules/ page whose stated version matches the
  rule and which links the canonical artifact, and every skill must have a
  README.md that links its SKILL.md. Orphan pages documenting a deleted
  artifact now fail the build.