test(chat): MCP 工具循环端到端测试

- tests/api/fake_openai.py：假 OpenAI 流式接口，先返回 tool_call 再返回文本
- tests/chattest.cpp：真实 ChatClient + McpManager 走完 请求→工具→回填→回答
- fix(mcp): 回调应收到 JSON-RPC 的 result，而不是整个响应包（否则工具结果为空）
- 两个无头测试均通过

CMakeLists.txt

@@ -74,6 +74,17 @@ add_executable(gxde-ai-see-selftest
 target_include_directories(gxde-ai-see-selftest PRIVATE src ${ICU_INCLUDE_DIRS})
 target_link_libraries(gxde-ai-see-selftest PRIVATE Qt6::Core Qt6::Gui ${ICU_LIBRARIES})
 
+add_executable(gxde-ai-see-chattest
+    tests/chattest.cpp
+    src/chat/chatclient.cpp
+    src/chat/mcpclient.cpp
+    src/config.cpp
+)
+target_include_directories(gxde-ai-see-chattest PRIVATE src)
+target_link_libraries(gxde-ai-see-chattest PRIVATE Qt6::Core Qt6::Network)
+target_compile_definitions(gxde-ai-see-chattest PRIVATE
+    TESTS_DIR="${CMAKE_CURRENT_SOURCE_DIR}/tests")
+
 add_executable(gxde-ai-see-mcptest
     tests/mcptest.cpp
     src/chat/mcpclient.cpp