Added foveated rendering for the Quest

- Eyes render under a VK_EXT_fragment_density_map: full rate around each eye's forward direction,
  2x2 then 4x4 pixel blocks towards the edges ([vr] foveation = off|low|medium|high, default off).
  XR_FB_foveation cannot help here: the runtime's maps only shape passes drawing into its
  swapchain, and the eyes reach it through a copy.
- aurora-main/patches/dawn/aurora_fdm.inc: Dawn enables the extension only on request and for
  dynamic rendering, flags every render pipeline, and chains an immutable RG8 map into any pass
  whose first color attachment is a view bound to one (ABI: include/aurora/dawn_fdm_abi.h).
- android/Build-QuestDawn.ps1 builds the pinned Dawn revision with those patches for arm64
  (dawn-build CI flags, protobuf off) into a cached package; Build-Quest.ps1 links it
  (-StockDawn opts out) and AuroraDawnProvider.cmake enables the ABI from its manifest.
- lib/gfx/foveation.hpp generates the maps (32 px per texel, densities 255/127/63); an eye is
  foveated only when single_pass_eyes draws it in one render pass. Menus never are.
- Live level from the headset panel's VR tab and the launcher; the launch decides whether the
  device has maps. debug.wiicompiled.foveation and debug.wiicompiled.fdm for A/B.
- Tests: Foveation cases in gx_fifo_tests, mkw_vr_config_tests. Docs: OPENXR.md, quest-port.md.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

runtime/src/settings_overlay.cpp

@@ -145,6 +145,11 @@ bool g_vrHudVirtualScreen = RuntimeConfigFile::VrHudVirtualScreen(true);
 bool g_vrFlatScreen = RuntimeConfigFile::VrFlatScreen();
 #if defined(__ANDROID__)
 bool g_vrPassthrough = RuntimeConfigFile::VrPassthrough();
+// Menu labels for the foveation levels, index-matched to RuntimeConfigFile::kVrFoveationLevels and to
+// aurora_set_stereo_foveation.
+constexpr std::array<const char*, 4> kVrFoveationLabels{"Off", "Low", "Medium", "High"};
+static_assert(kVrFoveationLabels.size() == RuntimeConfigFile::kVrFoveationLevels.size());
+int g_vrFoveation = static_cast<int>(RuntimeConfigFile::VrFoveationLevelIndex(RuntimeConfigFile::VrFoveation()));
 #endif
 bool g_vrFirstPerson = RuntimeConfigFile::VrFirstPerson(false);
 bool g_vrFirstPersonToggleClick = RuntimeConfigFile::VrFirstPersonToggleClick();
@@ -1512,6 +1517,25 @@ void DrawVrSettings() {
             "fully virtual; the Flat Screen race has the room around it too. "
             "Applies immediately.");
     }
+    // Shows the live level, which debug.wiicompiled.foveation can override.
+    g_vrFoveation = static_cast<int>(aurora_get_stereo_foveation());
+    if (ImGui::Combo("Foveated rendering", &g_vrFoveation, kVrFoveationLabels.data(),
+                     static_cast<int>(kVrFoveationLabels.size()))) {
+        aurora_set_stereo_foveation(static_cast<uint32_t>(g_vrFoveation));
+        RuntimeConfigFile::SetVrFoveation(
+            std::string(RuntimeConfigFile::kVrFoveationLevels[static_cast<size_t>(g_vrFoveation)]));
+    }
+    if (ImGui::IsItemHovered()) {
+        ImGui::SetTooltip(
+            "%s", aurora_stereo_foveation_available()
+                      ? "Shades the edges of the race view in 2x2, then 4x4 pixel blocks, where the "
+                        "lenses blur the picture anyway, to free GPU time for a higher render scale or a "
+                        "steadier frame rate. Higher levels start closer to the centre; High also "
+                        "coarsens the corners of the HUD. Menus are never foveated. Applies immediately."
+                      : "Shades the edges of the race view in 2x2, then 4x4 pixel blocks, where the "
+                        "lenses blur the picture anyway, to free GPU time. This session started with it "
+                        "off, or without a GPU that supports it: a new level applies after a restart.");
+    }
 #endif
     ImGui::Separator();
     ImGui::Text("VR camera");
@@ -2331,6 +2355,9 @@ void InitializeRuntimeSettings() noexcept {
     aurora_set_stereo_stop_at_display_copy(g_vrStopAtDisplayCopy);
     aurora_set_stereo_skip_copy_clears(g_vrSkipCopyClears);
     aurora_set_stereo_single_pass_eyes(g_vrSinglePassEyes);
+#if defined(__ANDROID__)
+    aurora_set_stereo_foveation(static_cast<uint32_t>(g_vrFoveation));
+#endif
     aurora_set_stereo_mirror_view(static_cast<AuroraStereoMirrorView>(g_vrMirrorView));
     mkw::vr::OpenXRSetControllerMode(static_cast<mkw::vr::OpenXRControllerMode>(g_vrControllerMode));
     ApplyVrHudVirtualScreen();