Implements: ag-btg.1
Validates contract-*.md files in .agents/specs/ against the Wave 1
consistency checklist: frontmatter completeness, structural completeness
(>=3 invariants, >=3 test rows, invariant references), scope consistency
(one contract per issue), and test readiness (success + error paths).
Placeholder and terminology checks emit WARN without blocking.
Includes test fixtures and test-gate.sh exercising each failure mode.
Boden Fuller