v0.3.0

Minor release — new-but-additive, nothing here requires action in an already-onboarded repo.

See CHANGELOG.md#030---2026-08-04 for the full list.

Highlights: check-followups.py, the long-range counterpart to check-follow-ups for stale open commitments; docs/GUARD.md and docs/AUDIT.md split out of the README; and four rounds of external-review polish — the Quickstart's clone-and-checkout example is now self-resolving, paste-and-run, and filtered to real semver tags, and the follow-up-ownership and enforcement-tier stories are stated once and consistently.