The coverage check read only line-rate, so a file could pass with weak
branch coverage. Load both Cobertura rates and fail any tracked file
below the 95% floor on either metric, failing closed when branch
evidence is absent. Prove enforcement end to end with a synthetic
fully-lined but branch-weak file failing run_profile.
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>