refactor(tests): reorganize tests into unittest/ and e2e/ directories

- Move all unit tests from tests/ to tests/unittest/
- Add tests/e2e/ directory for end-to-end tests
- Update conftest.py for new test structure
- Add new tests for auth dependencies, policies, route injection
- Add new tests for run callbacks, create store, execution artifacts
- Remove obsolete tests for deleted persistence layer

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

backend/tests/unittest/test_run_execution_artifacts.py

@@ -0,0 +1,26 @@
+from __future__ import annotations
+
+from deerflow.runtime.runs.internal.execution.artifacts import build_run_artifacts
+
+
+class _Agent:
+    pass
+
+
+def test_build_run_artifacts_uses_store_as_reference_store():
+    store = object()
+
+    def agent_factory(*, config):
+        return _Agent()
+
+    artifacts = build_run_artifacts(
+        thread_id="thread-1",
+        run_id="run-1",
+        checkpointer=None,
+        store=store,
+        agent_factory=agent_factory,
+        config={},
+        bridge=None,  # type: ignore[arg-type]
+    )
+
+    assert artifacts.reference_store is store