Adds EVENGINE_ANDROID_TEST_APP build mode: the unit_test sources are
compiled into libmain.so (SDL entry) and packaged by the existing Gradle
APK along with the test assets, so the full zeroerr suite can run on a
device via adb logcat.
- test/main.cpp: Android runner with LogcatBuf (cout/cerr -> logcat),
chdir to <files>/evengine_test, SDL_Init; keeps SDL_main symbol unmangled.
- test/PathBesideSource.h: shared pathBesideThisSource helper that maps
__FILE__ to the on-device unpacked tree on Android.
- EVTestActivity: unpacks assets/test + assets/examples to internal
storage and passes an optional --testcase filter from an intent extra.
- test/CMakeLists.txt: builds `main` instead of unit_test on Android,
excludes desktop-only devtools tests, links Android system libs.
- Makefile: build/android-debug-test, sync/android-test-assets,
run/android-test-debug, log/android-test targets.
- Gradle wrapper bumped to 8.5 for Java 21 compatibility.