Implement TEN-WP-0011 security layer conformance

Engine/PIP declaration is now checkable (layer.yaml plus a Tooling-client
scan). Writes persist a decision record or the published fail-closed
stance, live-lookup freshness is published, events_for is tenant-scoped,
and mutation evidence drains to audit-core from a local outbox without
blocking the mutation.

Sender registration is requested as AUDIT-IN-0002. Boundary-contract
amendment is requested as NET-IN-0002.

Assistant: grok
Assistant-Session: 01a04cea-e5e8-7081-a0fc-808ebbc35fa9

tests/helpers.py

@@ -0,0 +1,48 @@
+from tenant_engine.authz import (
+    AuthorizationOutcome,
+    WriteAuthorizationDeniedError,
+)
+
+
+class AllowAllAuthorizer:
+    """Test double: allow every action and leave a reconstructable decision record."""
+
+    def authorize(self, *, action: str, tenant_id: str, actor: str) -> AuthorizationOutcome:
+        return AuthorizationOutcome(
+            action=action,
+            tenant_id=tenant_id,
+            actor=actor,
+            allowed=True,
+            source="decision",
+            reason="test_allow_all",
+            decision_id="test:allow",
+            request_digest="test",
+            effect="allow",
+        )
+
+
+def deny(
+    action: str, tenant_id: str, actor: str, reason: str = "not permitted"
+) -> WriteAuthorizationDeniedError:
+    return WriteAuthorizationDeniedError(
+        AuthorizationOutcome(
+            action=action,
+            tenant_id=tenant_id,
+            actor=actor,
+            allowed=False,
+            source="decision",
+            reason=reason,
+            decision_id="test:deny",
+            effect="deny",
+        )
+    )
+
+
+class ScopedAuthorizer:
+    def __init__(self, *allowed: str) -> None:
+        self._allowed = set(allowed)
+
+    def authorize(self, *, action: str, tenant_id: str, actor: str) -> AuthorizationOutcome:
+        if action not in self._allowed:
+            raise deny(action, tenant_id, actor)
+        return AllowAllAuthorizer().authorize(action=action, tenant_id=tenant_id, actor=actor)