fix(startup): avoid reentrant Windows focus (#37)

- Keep the main WebView2 window unfocused during native construction.
- Remove the synchronous post-build focus request that caused the Windows stack overflow.
- Refs #37.

src-tauri/src/lib.rs

@@ -18518,22 +18518,15 @@ pub fn run() {
                 // newly-created host window is not focusable yet. Wry
                 // propagates that error from WebviewWindowBuilder::build,
                 // which destroys the native window and makes a release build
-                // look like it started headlessly before exiting. Focus the
-                // window only after WebView2 has been created successfully.
+                // look like it started headlessly before exiting. Leave the
+                // window unfocused until Windows has completed native
+                // activation; a synchronous post-build focus request can
+                // re-enter the WebView2 focus callback on affected systems.
                 main_window_builder = main_window_builder.focused(false);
             }
-            let main_window = main_window_builder
+            main_window_builder
                 .build()
                 .map_err(|error| format!("failed to create main window: {error}"))?;
-            #[cfg(target_os = "windows")]
-            if let Err(error) = main_window.set_focus() {
-                // The window is already usable if the OS declines this
-                // best-effort activation request. A later user interaction
-                // can focus it without risking startup failure.
-                log::warn!("could not focus the main window after startup: {error}");
-            }
-            #[cfg(not(target_os = "windows"))]
-            let _ = main_window;
             restore_pending_main_window(app.handle());
 
             #[cfg(any(target_os = "windows", target_os = "linux"))]