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>

aurora-main/lib/webgpu/fdm.cpp

@@ -0,0 +1,107 @@
+#include "fdm.hpp"
+
+#include "../internal.hpp"
+#include "gpu.hpp"
+
+#include <algorithm>
+#include <bit>
+
+// AURORA_DAWN_FDM carries the ABI version of the Dawn package's patches (AuroraDawnProvider.cmake).
+#if defined(__ANDROID__) && defined(AURORA_DAWN_FDM)
+#include <aurora/dawn_fdm_abi.h>
+static_assert(AURORA_DAWN_FDM == AURORA_DAWN_FDM_ABI,
+              "The Dawn package's fragment density map ABI does not match include/aurora/dawn_fdm_abi.h");
+#define AURORA_FDM_SUPPORTED 1
+#endif
+
+namespace aurora::webgpu::fdm {
+namespace {
+Module Log("aurora::webgpu::fdm");
+
+bool g_requested = false;
+bool g_available = false;
+uint32_t g_texelSize = 0;
+
+// Meta's own maps use 32: rings smooth enough, in a map of a few hundred texels.
+constexpr uint32_t kPreferredTexelSize = 32;
+} // namespace
+
+void request(bool wanted) noexcept {
+  g_requested = wanted;
+#ifdef AURORA_FDM_SUPPORTED
+  AuroraDawnFdmRequest(wanted ? 1 : 0);
+#endif
+}
+
+void device_created() noexcept {
+  g_available = false;
+  g_texelSize = 0;
+#ifdef AURORA_FDM_SUPPORTED
+  AuroraDawnFdmCaps caps{};
+  if (AuroraDawnFdmQuery(g_device.Get(), &caps) != 0) {
+    // Density texels cover a power-of-two area within the device's range in each direction.
+    const uint32_t smallest = std::max({caps.minTexelWidth, caps.minTexelHeight, 1u});
+    const uint32_t largest = std::max(std::min(caps.maxTexelWidth, caps.maxTexelHeight), smallest);
+    g_texelSize = std::bit_ceil(std::clamp(kPreferredTexelSize, smallest, largest));
+    g_available = true;
+    Log.info("Fragment density maps: enabled, {}x{} to {}x{} pixels per texel, using {}", caps.minTexelWidth,
+             caps.minTexelHeight, caps.maxTexelWidth, caps.maxTexelHeight, g_texelSize);
+  } else if (g_requested) {
+    Log.warn("Fragment density maps: unavailable; the device lacks VK_EXT_fragment_density_map for "
+             "non-subsampled images, or Dawn does not render through dynamic rendering");
+  }
+#else
+  if (g_requested) {
+    Log.warn("Fragment density maps: unavailable; this build links a Dawn without Aurora's patches "
+             "(android/Build-QuestDawn.ps1)");
+  }
+#endif
+}
+
+bool available() noexcept { return g_available; }
+
+uint32_t texel_size() noexcept { return g_texelSize; }
+
+uint64_t create_map(uint32_t width, uint32_t height, const uint8_t* rg8) noexcept {
+#ifdef AURORA_FDM_SUPPORTED
+  if (g_available) {
+    return AuroraDawnFdmCreateMap(g_device.Get(), width, height, rg8);
+  }
+#endif
+  (void)width;
+  (void)height;
+  (void)rg8;
+  return 0;
+}
+
+bool map_ready(uint64_t map) noexcept {
+#ifdef AURORA_FDM_SUPPORTED
+  if (g_available && map != 0) {
+    return AuroraDawnFdmMapReady(g_device.Get(), map) != 0;
+  }
+#endif
+  (void)map;
+  return false;
+}
+
+void release_map(uint64_t map) noexcept {
+#ifdef AURORA_FDM_SUPPORTED
+  if (g_available && map != 0) {
+    AuroraDawnFdmReleaseMap(g_device.Get(), map);
+  }
+#endif
+  (void)map;
+}
+
+bool bind(const wgpu::TextureView& view, uint64_t map) noexcept {
+#ifdef AURORA_FDM_SUPPORTED
+  if (g_available && view) {
+    return AuroraDawnFdmBind(g_device.Get(), view.Get(), map) != 0;
+  }
+#endif
+  (void)view;
+  (void)map;
+  return false;
+}
+
+} // namespace aurora::webgpu::fdm