Add standalone repro for the gioui activity-recreate hang

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).

scripts/repro_gioui_hang.sh

@@ -0,0 +1,102 @@
+#!/usr/bin/env bash
+# Reproduce the gioui Android activity-recreation hang with a STOCK gioui
+# example app (the "hello" example from gioui.org/example).
+#
+# What it does:
+#   1. Builds gioui.org/example's hello app (unmodified) with gogio.
+#   2. Installs it on an emulator (boots one if needed).
+#   3. Recreates the activity via `cmd uimode night yes` (uiMode is not in
+#      gioui's configChanges mask, so Android destroys/recreates the
+#      activity in the same process).
+#   4. Taps the app and checks logcat for NO_INPUT_CHANNEL.
+#
+# The bug (gioui v0.10.x, app/os_android.go onCreateView): on re-attach the
+# second onCreateView sends the window-creation ack
+# (mainWindow.windows <- struct{}{}) on the UI thread, but its only
+# receiver (newWindow in Window.init) never re-runs on Android — the driver
+# is never reset, so w.Event() never returns to re-init. The UI thread
+# blocks forever, the activity never attaches an input channel, and the app
+# is black and unresponsive (process still alive).
+#
+# Usage:
+#   scripts/repro_gioui_hang.sh [avd-name] [path-to-apk]
+#
+# Exit codes: 0 = bug REPRODUCED, 1 = not reproduced, 2 = setup failure.
+set -euo pipefail
+
+AVD=${1:-pad_avd}
+APK=${2:-}
+SDK=${ANDROID_HOME:-$HOME/android-sdk}
+export PATH=$PATH:$HOME/go/bin:$SDK/platform-tools:$SDK/build-tools/35.0.0
+
+say() { printf '\n=== %s\n' "$*"; }
+die() { say "FAIL: $*"; exit 2; }
+
+# --- 1. Build the stock hello example, unless an APK was supplied ---------
+if [ -z "$APK" ]; then
+  SRC=$(mktemp -d)
+  trap 'rm -rf "$SRC"' EXIT
+  say "building stock gioui.org/example hello app (v0.10.3)"
+  go mod download gioui.org/example@v0.10.3
+  cp "$HOME/go/pkg/mod/gioui.org/example@v0.10.3/hello/hello.go" "$SRC/main.go"
+  cat > "$SRC/go.mod" <<'EOF'
+module hello
+
+go 1.23
+
+require gioui.org v0.10.3
+EOF
+  (cd "$SRC" && go mod tidy && gogio -target android -targetsdk 34 -arch amd64 -o /tmp/hello-gioui-repro.apk .)
+  APK=/tmp/hello-gioui-repro.apk
+fi
+[ -f "$APK" ] || die "APK not found: $APK"
+
+# --- 2. Emulator: reuse a booted one or start $AVD ------------------------
+say "waiting for emulator (avd $AVD)"
+EMU=""
+for _ in $(seq 1 60); do
+  EMU=$(adb devices | awk '$1 ~ /^emulator-/ {print $1; exit}')
+  [ -n "$EMU" ] && break
+  emulator -avd "$AVD" -no-window -no-audio -no-boot-anim -gpu swiftshader_indirect >/dev/null 2>&1 &
+  sleep 5
+done
+[ -n "$EMU" ] || die "no emulator available"
+for _ in $(seq 1 60); do
+  bc=$(adb -s "$EMU" shell getprop sys.boot_completed 2>/dev/null | tr -d '\r')
+  [ "$bc" = "1" ] && break
+  sleep 5
+done
+[ "$(adb -s "$EMU" shell getprop sys.boot_completed | tr -d '\r')" = "1" ] || die "emulator did not boot"
+say "emulator: $EMU"
+
+# --- 3. Install + launch ---------------------------------------------------
+APPID=localhost.hello   # gogio's default app id for module "hello"
+adb -s "$EMU" install -r "$APK" >/dev/null
+adb -s "$EMU" shell am force-stop "$APPID" >/dev/null 2>&1 || true
+adb -s "$EMU" logcat -c
+adb -s "$EMU" shell am start -n "$APPID/org.gioui.GioActivity" >/dev/null
+sleep 5
+adb -s "$EMU" shell pidof "$APPID" >/dev/null || die "app did not start"
+say "baseline: app running"
+
+# --- 4. Recreate the activity ----------------------------------------------
+# uiMode is not in gioui's configChanges mask -> Android recreates the
+# activity. Force a real state change (a no-op toggle recreates nothing).
+cur=$(adb -s "$EMU" shell cmd uimode night | tr -d '\r')   # "Night mode: yes/no"
+case $cur in
+  *yes*) adb -s "$EMU" shell cmd uimode night no >/dev/null ;;
+  *)     adb -s "$EMU" shell cmd uimode night yes >/dev/null ;;
+esac
+sleep 5
+adb -s "$EMU" logcat -c
+adb -s "$EMU" shell input tap 540 1200
+sleep 2
+
+# --- 5. Verdict -------------------------------------------------------------
+adb -s "$EMU" exec-out screencap -p > /tmp/gioui-hang-repro.png
+if adb -s "$EMU" logcat -d | grep -q NO_INPUT_CHANNEL; then
+  say "REPRODUCED: activity recreation left the window with NO_INPUT_CHANNEL (see /tmp/gioui-hang-repro.png)"
+  exit 0
+fi
+say "NOT reproduced: no NO_INPUT_CHANNEL after recreation (gioui handles re-attach correctly)"
+exit 1