Harden coverage, error paths, and package verification

[noah-ing]

Summary

• enforce branch-enabled combined coverage in the authoritative Docker/CI smoke path, with an 85.00% floor chosen below the measured 85.66% baseline
• regression-test generic broker and inventory failure paths, signed fail-closed denials, leakage boundaries, and honest post-invocation MCP failures
• strengthen wheel/sdist verification with exact metadata, inventories, modes, RECORD integrity, forbidden-file exclusions, and an offline isolated wheel import

Verification

• host: 145 passed; 15 Linux-only swtpm tests deselected; 88.20% branch-enabled combined coverage
• clean no-cache Docker/Compose: 160 passed; zero skips/failures; 15 genuine real-swtpm tests; 90.33% coverage
• Ruff lint/format, Mypy (13 source files), Bandit, pip-audit, detect-secrets, uv lock, Compose config, package build/verifier, and offline isolated wheel install/import passed
• final independent source/security review: no actionable findings

Assurance boundary

This does not broaden the project claim. It does not establish bit reproducibility, hardware provenance, holder-key residency, TPM/agent co-location, agent execution, runtime integrity, safe behavior, or exactly-once business execution.