feat(vulkan): run the compute/UI path without VK_EXT_descriptor_heap

Device::Initialize required twelve device extensions with no capability
check. Mesa Turnip (Adreno) lacks six of them: VK_EXT_descriptor_heap,
VK_KHR_shader_untyped_pointers, VK_EXT_device_fault and the three ray
tracing extensions. vkCreateDevice failed there, so not even a UI-only
program could start, although the UI path is compute-only and needs
nothing else that Turnip is missing.

The descriptor heap, ray tracing and device fault are now optional
groups, detected at start-up from the extension list and the feature
bits (Device::descriptorHeapSupported, rayTracingSupported,
deviceFaultSupported). Ray tracing needs the heap; on a device without
it the ray tracing entry points throw a message naming the cause.

Without the heap the same bindless slots live in one update-after-bind
descriptor set per frame, owned by DescriptorHeapVulkan: binding 0
storage images, 1 sampled images, 2 samplers, 3 storage buffers. Slot
allocation, the slot handles, UIDispatchHeader and the UIRenderer API
are unchanged; buffer slots simply stop being offset. Window::Render
binds that frame's set where it binds the heap, every compute pipeline
shares the heap object's pipeline layout, and push data travels as push
constants.

Each UI kernel is built twice from one source. ui-shared.glsl declares
its resources through UI_HEAP_* macros that expand to descriptor_heap
or, with CRAFTER_GRAPHICS_DESCRIPTOR_SETS defined, to set/binding.
<name>.comp.spv and <name>.comp.sets.spv ship side by side and
ComputeShader::Load picks one. The heap build of every shader is
byte-identical to before.

Breaking:
- ComputeShader::Load takes the heap as a second argument.
- DescriptorHeapVulkan is no longer copyable or movable.
- Custom UI shaders declare heap resources with the UI_HEAP_* macros
  and are registered twice in project.cpp (see the README).
- project.cpp uses Shader::defines and Shader::variant, so it needs a
  crafter-build that has them (Crafter.Build master, fe38cc1 or later).

Also:
- maintenance5 is enabled as a feature, not only as an extension:
  every VulkanBuffer already relied on VkBufferUsageFlags2CreateInfo.
- Barrier stage masks drop RAY_TRACING_SHADER on devices without ray
  tracing, and ImageVulkan::Create resolves its default consumer stage
  to COMPUTE_SHADER there.
- Window refuses a swapchain whose image count is not numFrames
  instead of writing past images[]. The limitation itself is #160.
- CRAFTER_GRAPHICS_NO_DESCRIPTOR_HEAP forces the fallback on a driver
  that has the heap, so it can be exercised on a desktop GPU.

Verified on an RTX 4090 in both modes under the validation layer, and
on a Fairphone 6 (Turnip, Adreno 810, postmarketOS), where the fallback
is the only path.

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>

implementations/Crafter.Graphics-UI.cpp

@@ -30,11 +30,11 @@ void UIRenderer::Initialize(Window& window, GraphicsDescriptorHeap& heap, Graphi
     heap_   = &heap;
 
     // Load the four standard pipelines plus the fused uber-kernel (issue #47).
-    drawQuads.Load(quadsSpv);
-    drawCircles.Load(circlesSpv);
-    drawImages.Load(imagesSpv);
-    drawText.Load(textSpv);
-    drawFused.Load(fusedSpv);
+    drawQuads.Load(quadsSpv, heap);
+    drawCircles.Load(circlesSpv, heap);
+    drawImages.Load(imagesSpv, heap);
+    drawText.Load(textSpv, heap);
+    drawFused.Load(fusedSpv, heap);
 
     // Allocate one image slot for the swapchain output. Each per-frame heap
     // copy will hold ITS frame's image at this slot.
@@ -275,6 +275,16 @@ void UIRenderer::Dispatch(GraphicsCommandBuffer cmd, const GraphicsComputeShader
 // ─── descriptor writes ─────────────────────────────────────────────────
 
 void UIRenderer::WriteSwapchainDescriptors() {
+    if (!Device::descriptorHeapSupported) {
+        // Sets mode: each frame's descriptor set holds ITS swapchain image at
+        // outImageSlot_, through a view the heap object creates and owns.
+        for (std::uint8_t f = 0; f < Window::numFrames; ++f) {
+            heap_->WriteImageSet(f, outImageSlot_, VK_DESCRIPTOR_TYPE_STORAGE_IMAGE,
+                                 window_->imageViews[f], VK_IMAGE_LAYOUT_GENERAL);
+        }
+        return;
+    }
+
     // Each per-frame heap holds ITS swapchain image at outImageSlot_.
     std::array<VkImageDescriptorInfoEXT, Window::numFrames>    infos{};
     std::array<VkResourceDescriptorInfoEXT, Window::numFrames> resources{};
@@ -334,6 +344,11 @@ void UIRenderer::WriteFontAtlasDescriptor() {
 void UIRenderer::WriteSampledImageDescriptor(std::uint16_t slot,
                                              const VkImageViewCreateInfo& viewInfo,
                                              VkImageLayout layout) {
+    if (!Device::descriptorHeapSupported) {
+        heap_->WriteImageSets(slot, VK_DESCRIPTOR_TYPE_SAMPLED_IMAGE, viewInfo, layout);
+        return;
+    }
+
     std::array<VkImageDescriptorInfoEXT, Window::numFrames>    infos{};
     std::array<VkResourceDescriptorInfoEXT, Window::numFrames> resources{};
     std::array<VkHostAddressRangeEXT, Window::numFrames>       destinations{};
@@ -364,7 +379,14 @@ void UIRenderer::WriteSampledImageDescriptor(std::uint16_t slot,
     for (auto& h : heap_->resourceHeap) h.FlushDevice(off, sz);
 }
 
-void UIRenderer::WriteBufferDescriptor(std::uint16_t slot, VkDeviceAddress address, std::uint32_t size) {
+void UIRenderer::WriteBufferDescriptor(std::uint16_t slot, VkBuffer buffer, VkDeviceAddress address, std::uint32_t size) {
+    if (!Device::descriptorHeapSupported) {
+        // A descriptor set names the buffer by handle; the heap below names
+        // it by device address.
+        heap_->WriteBufferSets(slot, buffer);
+        return;
+    }
+
     std::array<VkDeviceAddressRangeEXT, Window::numFrames>     ranges{};
     std::array<VkResourceDescriptorInfoEXT, Window::numFrames> resources{};
     std::array<VkHostAddressRangeEXT, Window::numFrames>       destinations{};
@@ -393,6 +415,14 @@ void UIRenderer::WriteBufferDescriptor(std::uint16_t slot, VkDeviceAddress addre
 
 SamplerSlot UIRenderer::RegisterSampler(const VkSamplerCreateInfo& info) {
     auto range = heap_->AllocateSamplerSlots(1);
+    if (!Device::descriptorHeapSupported) {
+        // The handle owns the slot before the sampler is created, so a
+        // failed vkCreateSampler returns it to the freelist.
+        SamplerSlot slot{heap_, range.firstElement};
+        heap_->WriteSamplerSets(range.firstElement, info);
+        return slot;
+    }
+
     std::array<VkSamplerCreateInfo, Window::numFrames>   infos{};
     std::array<VkHostAddressRangeEXT, Window::numFrames> destinations{};
     for (std::uint32_t f = 0; f < Window::numFrames; ++f) {