Prevent first-keystroke UI stalls by suppressing WM_GETOBJECT on the launcher window

[Copilot]

Typing the first character could freeze Flow Launcher for ~15 seconds on affected systems. The stall was traced to the main WPF window servicing WM_GETOBJECT and entering the UI Automation provider path on the UI thread.

• Main window message handling

  • Intercept WM_GETOBJECT in MainWindow's existing HwndSource hook.
  • Mark the message as handled and return immediately so the launcher window does not enter WPF's synchronous automation-provider path during typing.
  • Scope is limited to the main search window; existing handling for other window messages remains unchanged.

• Behavioral boundary

  • Only WM_GETOBJECT is suppressed.
  • Other messages continue through the current WndProc switch unchanged.

• Regression coverage

  • Add a focused test that verifies the suppression predicate matches WM_GETOBJECT and does not suppress unrelated messages.

private const int WmGetObject = 0x003D;

private IntPtr WndProc(IntPtr hwnd, int msg, IntPtr wParam, IntPtr lParam, ref bool handled)
{
    if (msg == WmGetObject)
    {
        handled = true;
        return IntPtr.Zero;
    }

    // existing message handling...
}

• Fixes BUG: Flowlauncher freezing after typing in one character #4522