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/spec/template/base/base.j2

@@ -0,0 +1,7 @@
+{% if ifdef %}#ifdef {{ ifdef }}
+{% endif %}
+{% if ifndef %}#ifndef {{ ifndef }}
+{% endif %}
+{% block main %}{% endblock %}
+{% if ifdef %}#endif{% endif %}
+{% if ifndef %}#endif{% endif %}

android/gl4es-src/spec/template/base/copy_packed_call.j2

@@ -0,0 +1,13 @@
+packed_call_t* glCopyPackedCall(const packed_call_t *packed) {
+    switch (packed->format) {
+        {% for f in formats %}
+        case FORMAT_{{ f.types }}: {
+            int sizeofpacked = sizeof(PACKED_{{ f.types }});
+            PACKED_{{ f.types }} *newpacked = (PACKED_{{ f.types }}*)malloc(sizeofpacked);
+            memcpy(newpacked, packed, sizeofpacked);
+            return (packed_call_t*)newpacked;
+            break;
+        }
+        {% endfor %}
+    }
+}

android/gl4es-src/spec/template/base/fprint.j2

@@ -0,0 +1,5 @@
+{% if func.args %}
+    printf("{{ func.name }}({{ func.args|printf }});\n", {{ func.args|args(0) }});
+{% else %}
+    printf("{{ func.name }}();\n");
+{% endif %}

android/gl4es-src/spec/template/base/header.j2

@@ -0,0 +1,10 @@
+{% extends "base/base.j2" %}
+{% block main %}
+{% include "base/headers.j2" %}
+
+{% set guard = name.upper().replace('.', '_') -%}
+#ifndef {{ guard }}
+#define {{ guard }}
+{% block content %}{% endblock %}
+#endif
+{% endblock %}

android/gl4es-src/spec/template/base/headers.j2

@@ -0,0 +1,9 @@
+{% block headers %}
+{% for header in headers %}
+{% if "<" in header %}
+#include {{ header }}
+{% else %}
+#include "{{ header }}"
+{% endif %}
+{% endfor %}
+{% endblock %}

android/gl4es-src/spec/template/base/indexed_call.j2

@@ -0,0 +1,22 @@
+void glIndexedCall(const indexed_call_t *packed, void *ret_v) {
+    switch (packed->func) {
+        {% for f in functions %}
+        #ifndef skip_index_{{ f.name }}
+        case {{ f.name }}_INDEX: {
+            INDEXED_{{ f.types }} *unpacked = (INDEXED_{{ f.types }} *)packed;
+            {% if f.args %}
+            ARGS_{{ f.types }} args = unpacked->args;
+            {% endif %}
+            {% if not f.void %}
+            {{ f.return }} *ret = ({{ f.return }} *)ret_v;
+            *ret =
+            {% endif %}
+            {{ f.name }}({% for arg in f.args -%}
+                args.a{{ loop.index }}{% if not arg.last %}, {% endif %}
+            {% endfor %});
+            break;
+        }
+        #endif
+        {% endfor %}
+    }
+}

android/gl4es-src/spec/template/base/packed_call.j2

@@ -0,0 +1,16 @@
+void glPackedCall(const packed_call_t *packed) {
+    switch (packed->format) {
+        {% for f in formats %}
+        case FORMAT_{{ f.types }}: {
+            PACKED_{{ f.types }} *unpacked = (PACKED_{{ f.types }} *)packed;
+            {% if f.args %}
+            ARGS_{{ f.types }} args = unpacked->args;
+            {% endif %}
+            unpacked->func({% for arg in f.args -%}
+                args.a{{ loop.index }}{% if not arg.last %}, {% endif %}
+            {% endfor %});
+            break;
+        }
+        {% endfor %}
+    }
+}

android/gl4es-src/spec/template/base/wrap.c.j2

@@ -0,0 +1,16 @@
+{% extends "base/base.j2" %}
+{% block main %}
+{% include "base/headers.j2" %}
+{% for func in functions %}
+{% block definition scoped %}
+{{ func.return }} gl4es_{{ func.name }}({{ func.args|args }}) {
+    {% block load scoped %}{% endblock %}
+    {% block call scoped %}
+    {% if not func.void %}return {% endif %}{% block prefix %}wrap{% endblock %}_{{ func.name }}({{ func.args|args(0) }});
+    {%- endblock %}
+}
+{{ func.return }} {{ func.name }}({{ func.args|args }}) AliasExport("gl4es_{{ func.name }}");
+{% endblock %}
+{% endfor %}
+{% block content %}{% endblock %}
+{% endblock %}

android/gl4es-src/spec/template/base/wrap.h.j2

@@ -0,0 +1,65 @@
+{% extends "base/header.j2" %}
+{% block content %}
+
+typedef struct {
+    int format;
+    void *func;
+    void *args;
+} packed_call_t;
+
+typedef struct {
+    int func;
+    void *args;
+} indexed_call_t;
+
+enum FORMAT {
+{% for f in formats %}
+    FORMAT_{{ f.types }},
+{% endfor %}
+};
+
+{% for f in formats %}
+typedef {{ f.return }} (*FUNC_{{ f.types }})({{ f.args|args }});
+{% if f.args %}
+typedef struct {
+    {% for arg in f.args %}
+    {{ arg.type|unconst }} a{{ loop.index }}{% if arg.type == 'GLdouble' %} __attribute__ ((aligned(8))){% endif %};
+    {% endfor %}
+} ARGS_{{ f.types }};
+{% endif %}
+typedef struct {
+    int format;
+    FUNC_{{ f.types }} func;
+    {% if f.args %}
+    ARGS_{{ f.types }} args;
+    {% endif %}
+} PACKED_{{ f.types }};
+typedef struct {
+    int func;
+    {% if f.args %}
+    ARGS_{{ f.types }} args;
+    {% endif %}
+} INDEXED_{{ f.types }};
+{% endfor %}
+
+extern void glPushCall(void *data);
+void glPackedCall(const packed_call_t *packed);
+void glIndexedCall(const indexed_call_t *packed, void *ret_v);
+packed_call_t* glCopyPackedCall(const packed_call_t *packed);
+
+{% for func in functions %}
+#define {{ func.name }}_INDEX {{ loop.index }}
+#define {{ func.name }}_RETURN {{ func.return }}
+#define {{ func.name }}_ARG_NAMES {{ func.args|args(0) }}
+#define {{ func.name }}_ARG_EXPAND {{ func.args|args }}
+#define {{ func.name }}_PACKED PACKED_{{ func.types }}
+#define {{ func.name }}_INDEXED INDEXED_{{ func.types }}
+#define {{ func.name }}_FORMAT FORMAT_{{ func.types }}
+{% endfor %}
+
+{% for func in functions %}
+{{ func.return }} APIENTRY_GL4ES gl4es_{{ func.name }}({{ func.name }}_ARG_EXPAND);
+typedef {{ func.return }} (* APIENTRY_GLES {{ func.name }}_PTR)({{ func.name }}_ARG_EXPAND);
+{% endfor %}
+
+{% endblock %}