simplify queue ops, handle broken pipe errors

- Add OSError errno 32 (broken pipe) handling in progress broadcast
- Remove progress service calls from add/clear queue operations
- Add pending_by_episode cleanup on clear
- Update tests accordingly

tests/api/test_download_endpoints.py

@@ -246,7 +246,10 @@ async def test_remove_from_queue_single(
     """Test DELETE /api/queue/{item_id} endpoint."""
     response = await authenticated_client.delete("/api/queue/item-id-1")
 
-    assert response.status_code == 204
+    assert response.status_code == 200
+    data = response.json()
+    assert data["status"] == "success"
+    assert data["removed_id"] == "item-id-1"
 
     mock_download_service.remove_from_queue.assert_called_once_with(
         ["item-id-1"]
@@ -287,15 +290,15 @@ async def test_start_download_success(
 async def test_start_download_empty_queue(
     authenticated_client, mock_download_service
 ):
-    """Test starting download with empty queue returns 400."""
+    """Test starting download with empty queue returns 200 with info message."""
     mock_download_service.start_queue_processing.return_value = None
 
     response = await authenticated_client.post("/api/queue/start")
 
-    assert response.status_code == 400
+    assert response.status_code == 200
     data = response.json()
     message = data["message"].lower()
-    assert "empty" in message or "no pending" in message
+    assert "no pending" in message or "empty" in message
 
 
 @pytest.mark.asyncio