scripts/repro_gioui_hang.sh builds the stock gioui.org/example 'hello'
app (v0.10.3, unmodified source), installs it on an emulator, recreates
the activity with a real uiMode toggle, and checks for NO_INPUT_CHANNEL
after a tap. Exit 0 = bug reproduced, 1 = clean, 2 = setup failure.
The bug: gioui v0.10.x app/os_android.go onCreateView#2 sends the
window-creation ack (mainWindow.windows <- struct{}{}) on the UI thread
with no receiver (Window.init never re-runs on Android), blocking the UI
thread forever -> no input channel, black unresponsive app. The fix
lives in our gioui fork (only send the ack on first window creation).
