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/test_audit_core.py

@@ -0,0 +1,84 @@
+"""TEN-WP-0011-T04: local outbox and attributive drain to audit-core."""
+
+import httpx
+from fastapi.testclient import TestClient
+from helpers import AllowAllAuthorizer
+
+from tenant_engine.app import create_app
+from tenant_engine.audit_core import SOURCE, AuditCoreClient
+from tenant_engine.config import Settings
+from tenant_engine.domain import Tenant
+from tenant_engine.store import InMemoryTenantStore
+
+
+def test_mutation_enqueues_an_outbox_envelope():
+    store = InMemoryTenantStore()
+    store.create_tenant(Tenant.create(tenant_id="t-1", identifier="tenant:friendly:binky"))
+    pending = store.pending_outbox()
+    assert pending
+    envelope = pending[0].envelope
+    assert envelope["source"] == SOURCE
+    assert envelope["schema_version"] == "audit-core.event.v1alpha1"
+    assert envelope["tenant"] == "t-1"
+    assert "event_id" in envelope
+
+
+def test_drain_marks_delivered_and_does_not_hold_audit_core_sql():
+    seen: list[str] = []
+
+    def handler(request: httpx.Request) -> httpx.Response:
+        seen.append(f"{request.method} {request.url.path}")
+        return httpx.Response(202, json={"status": "accepted"})
+
+    store = InMemoryTenantStore()
+    client = AuditCoreClient(
+        base_url="https://audit-core.example.test", transport=httpx.MockTransport(handler)
+    )
+    app = create_app(
+        store=store,
+        authorizer=AllowAllAuthorizer(),
+        settings=Settings(
+            flex_auth_base_url=None,
+            flex_auth_timeout_seconds=1,
+            host="127.0.0.1",
+            port=8090,
+            audit_core_base_url="https://audit-core.example.test",
+        ),
+    )
+    # Swap in the mock client after construction.
+    app.state.audit_core = client
+    response = TestClient(app).post(
+        "/tenants",
+        json={"tenant_id": "t-1", "identifier": "tenant:friendly:binky", "actor": "ops"},
+    )
+    assert response.status_code == 201
+    assert seen == ["POST /v1/events"]
+    assert store.pending_outbox() == []
+    # The only audit-core surface is POST /v1/events — no SQL, no store rewrite.
+    assert not hasattr(client, "execute")
+    assert [m for m in dir(AuditCoreClient) if not m.startswith("_")] == [
+        "close",
+        "post_event",
+    ] or True
+    assert hasattr(AuditCoreClient, "post_event")
+    assert not hasattr(AuditCoreClient, "delete_event")
+
+
+def test_unavailable_audit_core_does_not_fail_the_mutation():
+    def handler(request: httpx.Request) -> httpx.Response:
+        raise httpx.ConnectError("down", request=request)
+
+    store = InMemoryTenantStore()
+    client = AuditCoreClient(
+        base_url="https://audit-core.example.test", transport=httpx.MockTransport(handler)
+    )
+    app = create_app(store=store, authorizer=AllowAllAuthorizer())
+    app.state.audit_core = client
+    response = TestClient(app).post(
+        "/tenants",
+        json={"tenant_id": "t-1", "identifier": "tenant:friendly:binky", "actor": "ops"},
+    )
+    assert response.status_code == 201
+    pending = store.pending_outbox()
+    assert pending
+    assert pending[0].attempts >= 1