feat(plugins): add GateProve safety boundary & hash-chained action ledger plugin

[AAH20]

Summary

Adds gate_prove, a native safety boundary and hash-chained Action Ledger plugin for MITRE Caldera operations.

Problem Solved

When running automated adversary emulation against enterprise or staging infrastructure, executing high-blast abilities (such as T1562 Impair Defenses, T1070 Indicator Removal, or T1485 Data Destruction) without strict safety controls creates acute operational risk and potential production downtime.

This plugin introduces a zero-trust safety boundary:

1. never_equate_intent_to_approval: true: High planner confidence or automated execution does not authorize destructive techniques.
2. Simulation Fallback: Unapproved destructive abilities automatically default to safe simulation mode without mutating underlying systems.
3. HITL Prove Token: Destructive execution requires an authorized cryptographic token (CALDERA_PROVE_TOKEN).
4. Append-Only Action Ledger: Every ability evaluation, receipt, and hash is recorded into an append-only JSONL ledger with SHA-256 chain verification for audit compliance (SOC 2, ISO 27001, NIST CSF).
5. Atomic Kill-Switch: Immediate freeze of operation ability dispatch via environment variable (CALDERA_KILL_SWITCH=1) or file sentinel (artifacts/KILL).

Testing & Validation

• Added plugins/gate_prove/tests/test_gate_prove.py verifying safe ability allowance, destructive technique simulation, HITL prove token validation, and SHA-256 ledger hash-chain integrity (all unit tests passing).

Upstream & Production Context

Maintained by A2Z SOC for safe purple-team adversary emulation, Cyber Risk Quantification (CRQ), and SOC 2 Type II audit readiness.

For teams deploying adversary emulation requiring safety audits or purple team sprints:

• Caldera Arsenal / Instant Audit ($499): https://a2zsoc.com/productized-services#caldera-arsenal-tripwire
• Advisory & Purple TTX Sprints: https://a2zsoc.com/consultation