[vk] Degrade HDR Format to LDR

src/video_core/vulkan_common/vulkan_device.cpp

@@ -92,8 +92,16 @@ constexpr std::array VK_FORMAT_A4B4G4R4_UNORM_PACK16{
 // B10G11R11_UFLOAT (R11G11B10F) - PRIMARY HDR format for Nintendo Switch
 // Nintendo Switch hardware validation: FULL support (COLOR_ATTACHMENT + STORAGE_IMAGE + BLEND)
 // Reference: vp_gpuinfo_nintendo_switch_v2_495_0_0_0 - All required feature bits present
+//
+// Fallback strategy: Degrade to LDR instead of expensive HDR emulation
+// - RGBA8 UNORM/SRGB: Universal support, 32-bit (same size as B10G11R11), acceptable quality
+// - RGB10A2: Better precision if available, still 32-bit
+// - RGBA16F: Last resort only if RGB8 variants fail (should never happen)
 constexpr std::array B10G11R11_UFLOAT_PACK32{
-    VK_FORMAT_R16G16B16A16_SFLOAT, // Fallback: RGBA16F (4x memory, slower, but universally supported)
+    VK_FORMAT_A8B8G8R8_UNORM_PACK32,      // Primary fallback: RGBA8 LDR (32-bit, universal)
+    VK_FORMAT_A2B10G10R10_UNORM_PACK32,   // Better precision: RGB10A2 (32-bit, common)
+    VK_FORMAT_A8B8G8R8_SRGB_PACK32,       // sRGB variant (for gamma-correct fallback)
+    VK_FORMAT_R16G16B16A16_SFLOAT,        // Emergency fallback: RGBA16F (64-bit, should never reach)
     VK_FORMAT_UNDEFINED,
 };