fix: don't start the app from main() on android; use the real inset retry

main() must not run real_main on android. The library's DT_INIT points at Odin's
_odin_entry_point, which the loader runs the moment NativeActivity dlopens
libmain.so -- before the glue calls android_main, so context.user_ptr is nil and
backend_init faults writing app.onAppCmd. The proc still has to exist: package
main requires it and it is the desktop entry point.

The insets retry now uses request_render_at. A plain request_render made before
the build is consumed by the frame it is running in, so it schedules nothing and
the loop parks with insets unresolved; it only appeared to work because the
first frames redraw anyway while the tree settles.

Guards the JNI-only paths (show_toast, refresh_insets) behind the android
subtarget so the shared real_main is usable on desktop. refresh_insets returns
true there rather than false: zero insets are correct where there are no system
bars, and returning false would retry every frame forever.

Also declares appCategory=game, and enables the engine's frame timings.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

android/AndroidManifest.xml

@@ -13,10 +13,11 @@
 
   <application
       android:label="Dogfooding"
+      android:appCategory="game"
       android:hasCode="false"
       android:icon="@mipmap/ic_launcher"
       android:roundIcon="@mipmap/ic_launcher_round"
-      android:debuggable="false">
+      android:debuggable="true">
 
     <activity android:name="android.app.NativeActivity"
               android:configChanges="orientation|keyboardHidden"