test: hard-fail the suite when the tenant resolves to production

Session-scoped autouse guard in tests/conftest.py refuses to run any
test (pytest.exit, returncode 1) when the effective tenant resolves
to the production tenant jpmschweitzer - the same guard library-desk
applies on its side. _initialize_app now depends on the guard so the
refusal happens before any initialization.

Suite-level assertions pin that the live session runs under the
llm_tester namespaces: Qdrant memories_llm_tester collection and
Redis session:llm_tester:* keys. The biographer/memory unit tests
already run fully mocked (no shared-service writes); the e2e
isolation tests already used llm_tester - their constants now derive
from the shared TEST_TENANT/PRODUCTION_TENANT config constants so a
drift fails loudly instead of silently splitting.

Verified: ENVIRONMENT=production pytest run exits 1 with the TENANT
GUARD message and zero tests executed.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

tests/core/test_tenant_guard.py

@@ -141,6 +141,44 @@ class TestRequestContextGuard:
             assert get_user() == "alice"
 
 
+@pytest.mark.unit
+class TestSuiteRunsUnderTestTenant:
+    """
+    The live test session itself must resolve to the test tenant.
+
+    The session guard in tests/conftest.py hard-fails the suite when the
+    effective tenant is the production tenant; these tests assert the
+    namespaces every shared-service touch would use (Qdrant memories
+    collection, Redis session keys) are the llm_tester ones.
+    """
+
+    def test_effective_tenant_is_not_production(self):
+        from src.core.context import get_default_user
+
+        assert get_default_user() != PRODUCTION_TENANT
+
+    def test_effective_tenant_is_the_reserved_test_tenant(self):
+        from src.core.context import get_default_user
+
+        assert get_default_user() == TEST_TENANT
+
+    def test_memories_collection_namespace_is_test_tenant(self):
+        from src.core.context import get_default_user
+        from src.core.multi_tenancy import get_memory_collection_name
+
+        assert (
+            get_memory_collection_name(get_default_user())
+            == f"memories_{TEST_TENANT}"
+        )
+
+    def test_redis_session_namespace_is_test_tenant(self):
+        from src.core.context import get_default_user
+        from src.core.multi_tenancy import get_session_key
+
+        key = get_session_key(get_default_user(), "conv_test")
+        assert key.startswith(f"session:{TEST_TENANT}:")
+
+
 @pytest.mark.unit
 class TestStartupTenantGuardLog:
     """One loud startup log line states the effective tenant."""