fix(server): 关闭 Direct2D 设置窗口后悬浮工具栏不再消失 (#1002)

Direct2D 设置窗口是获得键盘焦点的 Win32 窗口，进程里的 TIP 会成为普通输入客户端。
正常退出时 DestroyWindow / CoUninitialize 让 TSF 反激活 TIP，发出终结性反激活，
Server 当成用户切走了输入法而隐藏工具栏；回到的窗口不一定重新激活，工具栏要等
点击别的窗口才回来。WebView2 前端的焦点在 WebView 子进程里，宿主线程从不持有路由，
所以没有这个问题。

Direct2D 前端在写入排空后不再销毁窗口、跳过 CoUninitialize，直接结束进程：
Server 只看到管道断开（仅挂起路由，不动工具栏），与 WebView2 前端一致。

server/src/settings/settings_app.cpp

@@ -2453,7 +2453,14 @@ LRESULT CALLBACK WindowProc(HWND hwnd, UINT message, WPARAM w_param, LPARAM l_pa
         {
             g_worker->Drain(!g_closing);
             if (g_closing && g_worker->Stopped())
-                DestroyWindow(hwnd);
+            {
+                // The Direct2D frontend leaves without destroying its window: see the
+                // end of wWinMain for why the process must skip the TSF teardown.
+                if (g_native)
+                    PostQuitMessage(0);
+                else
+                    DestroyWindow(hwnd);
+            }
         }
         return 0;
     case WM_CLOSE:
@@ -2649,7 +2656,10 @@ int WINAPI wWinMain(HINSTANCE instance, HINSTANCE, PWSTR command_line, int show_
         DispatchMessageW(&message);
     }
     g_worker.reset(); // Drain accepted writes even if the window was destroyed externally.
-    CoUninitialize();
+    // The Direct2D frontend skips CoUninitialize like it skips DestroyWindow: both tear
+    // down this thread's TSF state (see below).
+    if (!use_native)
+        CoUninitialize();
     if (g_relaunch_after_exit)
     {
         // The renderer was switched: reopen in it once this instance no longer holds the
@@ -2663,5 +2673,18 @@ int WINAPI wWinMain(HINSTANCE instance, HINSTANCE, PWSTR command_line, int show_
             ShellExecuteW(nullptr, L"open", module_path.c_str(), nullptr, nullptr, SW_SHOWNORMAL);
         }
     }
+    if (use_native)
+    {
+        // The Direct2D window is a focused Win32 window, so this thread is an ordinary
+        // input client of the IME. Destroying the window or uninitializing COM lets TSF
+        // deactivate the text service here, which reports a terminal deactivation, and
+        // the Server hides the floating toolbar as if the user had switched input
+        // methods. The window the user returns to may not re-activate, so the toolbar
+        // stayed hidden until they clicked elsewhere. Every write has been drained
+        // above; end the process without that teardown, so the Server only sees the
+        // pipes close (a route suspension, which leaves the toolbar alone), as it does
+        // for the WebView2 frontend.
+        TerminateProcess(GetCurrentProcess(), static_cast<UINT>(message.wParam));
+    }
     return static_cast<int>(message.wParam);
 }