Fix activity-recreation crash: give Permissions a no-arg constructor

On any activity recreation with saved state (config changes such as
night mode), the FragmentManager restores the Permissions fragment
reflectively and requires a no-arg constructor; it only had
Permissions(View), so the activity failed to start with
Fragment$InstantiationException.

Also regenerate cmd/pad/Permissions.jar from the .java source in both
build scripts: gogio does not compile the app's own .java files - it
silently merges any *.jar in the Go package dirs into the dex, so the
stale Aug-16 jar shadowed source edits (which is how this bug went
unnoticed).

This crash is separate from the black-screen hang after relaunch,
which is fixed in the gioui fork (app/os_android.go: skip the window
handshake ack on re-attach).

cmd/pad/Permissions.java

@@ -25,6 +25,17 @@ public class Permissions extends Fragment {
 	Handler handler;
 	final int PERMISSIONS_REQUEST = 1;
 
+	// No-arg constructor required by the FragmentManager when restoring
+	// this fragment from the activity's saved state (activity recreation
+	// on config changes). Without it the restore throws
+	// Fragment$InstantiationException and the activity fails to start.
+	// Only the first-creation path uses the (View) constructor below;
+	// on restore the framework adds the fragment itself, and ctx/handler
+	// stay null — onAttach uses its own context parameter, so nothing on
+	// the restore path needs them.
+	public Permissions() {
+	}
+
 	public Permissions(View view) {
 		Log.d("gio", "Permissions()");
 		this.ctx = view.getContext();

scripts/build_emu.sh

@@ -54,6 +54,23 @@ fi
 WORK=$(mktemp -d)
 trap 'rm -rf "$WORK"' EXIT
 
+echo "=== compile Permissions.java -> Permissions.jar ==="
+# gogio does NOT compile the app's own .java files; it silently merges any
+# *.jar found in the Go package dirs (extraJars) into the dex. The
+# Permissions fragment is therefore shipped from cmd/pad/Permissions.jar.
+# Regenerate it from the .java source on every build, or source edits are
+# silently ignored (the stale jar wins) — that is how the missing no-arg
+# constructor (Fragment$InstantiationException on activity recreation) went
+# unnoticed.
+ANDROID_JAR="$ANDROID_HOME/platforms/android-35/android.jar"
+[ -f "$ANDROID_JAR" ] || die "android.jar missing: $ANDROID_JAR"
+PERMCLS=$(mktemp -d)
+javac -source 1.8 -target 1.8 -nowarn \
+	-bootclasspath "$ANDROID_JAR" \
+	-d "$PERMCLS" "$REPO/cmd/pad/Permissions.java" || die "Permissions.java failed to compile"
+jar cf "$REPO/cmd/pad/Permissions.jar" -C "$PERMCLS" st
+rm -rf "$PERMCLS"
+
 echo "=== gogio (Go -> APK) ==="
 # targetSdk 34: targeting 35 makes Android 15 force edge-to-edge. We keep 34
 # and instead consume the IME insets ourselves (PadInsetsListener patch below);

scripts/build_phone.sh

@@ -52,6 +52,23 @@ fi
 WORK=$(mktemp -d)
 trap 'rm -rf "$WORK"' EXIT
 
+echo "=== compile Permissions.java -> Permissions.jar ==="
+# gogio does NOT compile the app's own .java files; it silently merges any
+# *.jar found in the Go package dirs (extraJars) into the dex. The
+# Permissions fragment is therefore shipped from cmd/pad/Permissions.jar.
+# Regenerate it from the .java source on every build, or source edits are
+# silently ignored (the stale jar wins) — that is how the missing no-arg
+# constructor (Fragment$InstantiationException on activity recreation) went
+# unnoticed.
+ANDROID_JAR="$ANDROID_HOME/platforms/android-35/android.jar"
+[ -f "$ANDROID_JAR" ] || die "android.jar missing: $ANDROID_JAR"
+PERMCLS=$(mktemp -d)
+javac -source 1.8 -target 1.8 -nowarn \
+	-bootclasspath "$ANDROID_JAR" \
+	-d "$PERMCLS" "$REPO/cmd/pad/Permissions.java" || die "Permissions.java failed to compile"
+jar cf "$REPO/cmd/pad/Permissions.jar" -C "$PERMCLS" st
+rm -rf "$PERMCLS"
+
 echo "=== gogio (Go -> APK, arm64+arm) ==="
 # targetSdk 34: targeting 35 makes Android 15 force edge-to-edge. We keep 34
 # and instead consume the IME insets ourselves (PadInsetsListener patch below);