feat(WARDEN-WP-0015): T2 — machine-readable posture descriptors + warden policy
Adds registry/policy/security-posture.yaml (Axis A env postures, Axis B
maturity levels M0-M3, dataclass_floor, lattice rule — no secret
material) and src/warden/posture.py: typed loader with validation
(unique/contiguous ranks, floor references known levels) and the pure
can_deliver() lattice helper (no-write-down: prod posture + workload
maturity >= secret required_maturity + dataclass floor). New `warden
policy list|show` read-only lookup mirroring `warden route`.
tests/test_posture.py covers load, the allow/deny lattice matrix,
validation rejections, and CLI. 184 passed, lint clean.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
tegwick
0812d7303d