Add controller input and a laser-pointer-driven menu quad

- xr_input.c/h: an OpenXR action set (aim pose, trigger/select click, a
  menu-toggle button) plus ray/quad hit-testing, and a visible
  laser-pointer line drawn from the controller toward the hit point.
- xr_menu.c/h + MenuOverlay.java: a second composition-layer quad,
  toggled by a controller button, showing an off-screen, never-attached
  Android View tree (one "Keyboard" button so far) driven by synthetic
  touch events computed from the laser ray's hit UV.
- Migrate gl4es from a prebuilt binary baked into the Docker build-image
  to a vendored source snapshot (android/gl4es-src/) compiled from
  source at APK build time via CMake add_subdirectory(), patched through
  a new android/gl4es-patches/ (mirrors the existing engine-patches/
  pattern). This was needed to track down and fix a bug hit while
  building the menu: gl4es's fixed-pipeline emulation (fpe.c) was
  unconditionally substituting its own shader onto the menu's draw call
  (fpe_ReleventState() always sets alphafunc to a nonzero sentinel, so
  its fpe_IsEmpty() check could never see the state as empty), making
  the menu quad show the game's own rendering instead of its own
  content. Fixed by routing the menu's blit through a real
  glBlitFramebuffer() call instead of a shader-based draw, which gl4es's
  fpe.c has nothing to intercept - documented in README.md's new
  "Debugging notes" section.
- Renumber android/engine-patches/ to close the gap left by removing an
  unrelated diagnostic-only patch, and strip investigation-journal
  comments and dead diagnostic code (temporary tracing, env-var probes)
  left over from finding the bug above.
- Restructure README.md into numbered sections, document every
  engine/gl4es patch, add Android Studio dev/testing-cycle instructions,
  and generalize Quest-specific wording to any OpenXR headset. Update
  NOTICE.txt to match (gl4es is now vendored/patched source, not a
  prebuilt binary; add the OpenXR-SDK loader).

android/gl4es-src/Android.mk

@@ -0,0 +1,104 @@
+LOCAL_PATH := $(call my-dir)
+
+###########################
+#
+# GL static library
+#
+###########################
+
+include $(CLEAR_VARS)
+
+LOCAL_MODULE := GL
+
+LOCAL_C_INCLUDES := $(LOCAL_PATH)/include
+
+LOCAL_EXPORT_C_INCLUDES := $(LOCAL_C_INCLUDES) -DBCMHOST
+
+LOCAL_SRC_FILES := \
+	src/gl/arbconverter.c \
+	src/gl/arbgenerator.c \
+	src/gl/arbhelper.c \
+	src/gl/arbparser.c \
+	src/gl/array.c \
+	src/gl/blend.c \
+	src/gl/blit.c \
+	src/gl/buffers.c \
+	src/gl/build_info.c \
+	src/gl/debug.c \
+	src/gl/decompress.c \
+	src/gl/depth.c \
+	src/gl/directstate.c \
+	src/gl/drawing.c \
+	src/gl/enable.c \
+	src/gl/envvars.c \
+	src/gl/eval.c \
+	src/gl/face.c \
+	src/gl/fog.c \
+	src/gl/fpe.c \
+	src/gl/fpe_cache.c \
+	src/gl/fpe_shader.c \
+	src/gl/framebuffers.c \
+	src/gl/gl_lookup.c \
+	src/gl/getter.c \
+	src/gl/gl4es.c \
+	src/gl/glstate.c \
+	src/gl/hint.c \
+	src/gl/init.c \
+	src/gl/light.c \
+	src/gl/line.c \
+	src/gl/list.c \
+	src/gl/listdraw.c \
+	src/gl/listrl.c \
+	src/gl/loader.c \
+	src/gl/logs.c \
+	src/gl/matrix.c \
+	src/gl/matvec.c \
+	src/gl/oldprogram.c \
+	src/gl/pixel.c \
+	src/gl/planes.c \
+	src/gl/pointsprite.c \
+	src/gl/preproc.c \
+	src/gl/program.c \
+	src/gl/queries.c \
+	src/gl/raster.c \
+	src/gl/render.c \
+	src/gl/samplers.c \
+	src/gl/shader.c \
+	src/gl/shaderconv.c \
+	src/gl/shader_hacks.c \
+	src/gl/stack.c \
+	src/gl/stencil.c \
+	src/gl/string_utils.c \
+	src/gl/stubs.c \
+	src/gl/texenv.c \
+	src/gl/texgen.c \
+	src/gl/texture.c \
+	src/gl/texture_compressed.c \
+	src/gl/texture_params.c \
+	src/gl/texture_read.c \
+	src/gl/texture_3d.c \
+	src/gl/uniform.c \
+	src/gl/vertexattrib.c \
+	src/gl/wrap/gl4eswraps.c \
+	src/gl/wrap/gles.c \
+	src/gl/wrap/glstub.c \
+	src/gl/math/matheval.c \
+	src/glx/hardext.c \
+	src/glx/glx.c \
+	src/glx/lookup.c \
+	src/glx/gbm.c \
+	src/glx/streaming.c \
+
+LOCAL_CFLAGS += -g -std=gnu99 -funwind-tables -O3 -fvisibility=hidden -include include/android_debug.h
+LOCAL_CFLAGS += -DNOX11
+LOCAL_CFLAGS += -DNO_GBM
+#LOCAL_CFLAGS += -DNO_INIT_CONSTRUCTOR
+LOCAL_CFLAGS += -DDEFAULT_ES=2
+//TODO: maybe temporary?
+LOCAL_CFLAGS += -Wno-typedef-redefinition -Wno-dangling-else
+
+LOCAL_LDLIBS := -llog
+#building as a static lib
+
+LOCAL_CFLAGS += -DSTATICLIB
+include $(BUILD_STATIC_LIBRARY)