feat(P1): kyverno-json engine core + PolicyEngine protocol (REQ-291..294, 308, 309)

core/policy_engine.py: PolicyEngine Protocol (PEP 544, runtime_checkable)
+ PolicyEngineRegistry (selects from config.json.policy.engine) + NullEngine
fallback (NULL_ENGINE_INACTIVE when policy key absent).

adapters/kyverno-json/: KyvernoJsonEngine — shells to , translates
native output → list[dict] PCR records (engine: "kyverno", ruleId KJ_ prefix,
severity via nova.cloudinit.dev/severity annotation, default info).
is_configured() guards on  → KJ_ENGINE_NOT_CONFIGURED SKIPPED PCR
(distinct from NullEngine). Defensive parsing (malformed → error PCR).

config.json: new  object {engine: kyverno-json, policy_root}.

scripts/install-kyverno-json.sh: go install kj@latest (D-115).
CI (.gitea + .github): install Go + kj for policy-engine tests (best-effort;
tests skip when kj absent).

tests: 24 pass, 2 skip (kj not installed). 132 existing tests unchanged.
NullEngine satisfies PolicyEngine Protocol (G-Q8a — proves swap boundary).

---ci---
project: acdl
phase: 1
milestone: v1.25
status: execute
phase_role: execution
requirements:
  covered: [REQ-291, REQ-292, REQ-293, REQ-294, REQ-308, REQ-309]
  partial: []
---/ci---

.ciagent/config.json

@@ -209,5 +209,9 @@
     "enabled": true,
     "persist": true
   },
-  "strategic_direction_file": ".ciagent/NORTH_STAR.md"
+  "strategic_direction_file": ".ciagent/NORTH_STAR.md",
+  "policy": {
+    "engine": "kyverno-json",
+    "policy_root": "adapters/kyverno-json/policies"
+  }
 }