PR closes the M170 thread end-to-end:
#1961 spec → #1962 supersede → #1968 check (WARN) → this PR (sweep + STRICT).
Once merged, the floor consistency test in tests/manifests/test-cc-version-floor.sh defaults to STRICT mode — future PRs cannot ship a skill whose compatibility: floor is below the project SoT (currently 2.1.139).