feat: Phase B B4 certificate release-status schema

[cschanhniem]

Summary

• Adds CRS- certificate release-status schema (src/openamp_foundry/evidence/certificate_release_status.py)
• Tracks staged release lifecycle: draft → internal_review → external_review_ready → released → archived
• release_stage_index auto-computed from STAGED_RELEASE_ORDER; mismatch validation prevents inconsistency
• srd_authorized gate condition required before released status — links to E4 SRD- authorization chain
• can_advance_to() utility for checking valid stage transitions
• 60 tests; BASELINE updated 10974→11034; B4 marked complete in NEXT_100_PR_MAP.md

Design

• STAGED_RELEASE_ORDER: immutable progression order (draft=0, internal=1, external=2, released=3, archived=4)
• VALID_GATE_CONDITIONS: 8-value controlled vocabulary of gates that can be satisfied
• Backward transitions allowed (review → draft) but archived is terminal (no transitions out)
• released status requires srd_authorized gate — cannot release without E4 safety decision
• dry_lab_only=True always enforced

Safety

• Prevents bypassing review stages: released requires SRD- authorization
• Integrates with E4 safety-release decision via srd_authorized gate condition
• Marks B4 complete in NEXT_100_PR_MAP.md

Test plan

• 60 unit tests pass (constants, build, validate, can_advance_to, format)
• BASELINE regression test passes (11034)