fix: resolve ruff lint errors in Phase 2 code

- Move intent imports to TYPE_CHECKING block in graph.py (TC001)
- Rename test classes to CapWords convention (N801)
- Fix line length violations across test files (E501)
- Auto-fix import sorting (I001)

backend/tests/integration/test_websocket.py

@@ -19,7 +19,6 @@ from app.interrupt_manager import InterruptManager
 from app.session_manager import SessionManager
 from app.ws_handler import dispatch_message
 
-
 # ---------------------------------------------------------------------------
 # Helpers
 # ---------------------------------------------------------------------------
@@ -182,7 +181,8 @@ class TestWebSocketInterruptApproval:
     @pytest.mark.asyncio
     async def test_interrupt_then_approve(self) -> None:
         st_int = _state(interrupt=True, data={"action": "cancel_order", "order_id": "1042"})
-        g = _graph(chunks=[], st=st_int, resume_chunks=[_chunk("Order 1042 cancelled.", "order_actions")])
+        resume = [_chunk("Order 1042 cancelled.", "order_actions")]
+        g = _graph(chunks=[], st=st_int, resume_chunks=resume)
         g_, sm, im, cb, ws = _setup(graph=g)
 
         # Send message -> triggers interrupt
@@ -209,7 +209,8 @@ class TestWebSocketInterruptApproval:
     @pytest.mark.asyncio
     async def test_interrupt_then_reject(self) -> None:
         st_int = _state(interrupt=True)
-        g = _graph(chunks=[], st=st_int, resume_chunks=[_chunk("Order remains active.", "order_actions")])
+        resume = [_chunk("Order remains active.", "order_actions")]
+        g = _graph(chunks=[], st=st_int, resume_chunks=resume)
         g_, sm, im, cb, ws = _setup(graph=g)
 
         await _send(ws, g_, sm, im, cb, content="Cancel order 1042")