v0.4.9

Two build-lane fixes for the migration-reversibility churn observed on a live F1 run.

Fix 1 — prevent at authoring: the build-lane RED authoring directive now injects a migration-reversibility clause so the Navigator authors the test with an explicit down_revision round-trip, @pytest.mark.migration, and schema-recreation (not data-survival) on the first pass — in lockstep with checkTestlistMigrationRevision. The full canon already lived in navigator.md, but a cheaper red-turn model skipped it and authored a blind/dynamic downgrade base.

Fix 2 — stop the churn: the migration-reversibility test-smells (reversible-invariant-round-trip, relative-migration-revision, migration-marker-presence) are classified as author-layer smells a surgical Driver repair cannot close, and now short-circuit to a first-failure escalation with the remediation instead of burning bounded assess→repair rounds that can never green the test. Surgical smells stay on the assess→repair path.

Pins scm-utils 0.3.1.