fix: use 204 for DELETE response in contract and mock

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: kevinccbsg

contracts/todos-3.0.json

@@ -64,9 +64,8 @@
           }
         ],
         "responses": {
-          "200": {
-            "description": "Todo deleted",
-            "content": {}
+          "204": {
+            "description": "Todo deleted"
           }
         }
       }

src/twd-tests/todoList.twd.test.ts

@@ -93,7 +93,7 @@ describe("Todo List Page", () => {
       method: "DELETE",
       url: "/api/todos/1",
       response: null,
-      status: 200,
+      status: 204,
     });
     await twd.mockRequest("getTodoList", {
       method: "GET",