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/app/src/main/cpp/xr_mouse.h

@@ -21,8 +21,9 @@ extern "C" {
 void xr_mouse_move(int x, int y);
 
 // Pushes a synthetic SDL_MOUSEBUTTONDOWN/UP (SDL_BUTTON_LEFT) - matches
-// KeyboardOverlay's nativeSendPrintableChar() in questshock_native.c: a
-// plain SDL_Event built by hand and handed to the public SDL_PushEvent(),
+// KeyboardOverlay's nativeSendPrintableCharDown()/Up() in
+// questshock_native.c: a plain SDL_Event built by hand and handed to the
+// public SDL_PushEvent(),
 // no engine patch needed. pump_events() (sdl_events.c) reads whatever
 // mouse_put_xy() last set, not any x/y carried on the event itself - call
 // xr_mouse_move() first if position needs updating this frame.