Fix 3D texture corruption and stuck/dead-key input bugs

Stale GL_UNPACK state in gl4es and a missing pre-release GPU sync
caused diagonal-banded corruption in the 3D view. Synthetic key
press/release must track the real controller button or touch down/up
edges, not fire together in one call - fixes a typed movement key
sticking forever, then a follow-up that had silently broken A-button
jump and on-screen keyboard arrow keys. Also adds force-rebuild.sh for
the known stageEngine stale-cache issue.

android/force-rebuild.sh

@@ -0,0 +1,28 @@
+#!/usr/bin/env bash
+# Forces a fully fresh native build - works around stageEngine sometimes
+# wrongly reporting UP-TO-DATE after android/engine-patches/ or
+# android/gl4es-patches/ changes (see gradle_stage_engine_stale_cache memory
+# note). Run from anywhere. Needs JAVA_HOME set to a JDK 17+; defaults to
+# Android Studio's bundled JDK if found.
+set -euo pipefail
+
+SCRIPT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
+cd "$SCRIPT_DIR"
+
+if [ -z "${JAVA_HOME:-}" ]; then
+    if [ -d /opt/android-studio/jbr ]; then
+        export JAVA_HOME=/opt/android-studio/jbr
+    else
+        echo "JAVA_HOME not set and no JDK found at /opt/android-studio/jbr - export it yourself" >&2
+        exit 1
+    fi
+fi
+
+./gradlew --stop
+rm -rf \
+    ../build/android-engine \
+    ../build/android-gl4es \
+    ../build/android-prebuilt \
+    app/.cxx \
+    app/build
+echo "Done - next Gradle build/Run will rebuild from scratch."