fix(device): add preferred mask + required-only fallback to GetMemoryType (#59)

GetMemoryType was a bare first-superset match that threw whenever no
memory type satisfied the requested property flags. Callers combining a
mandatory flag with a perf-only one (HOST_VISIBLE | DEVICE_LOCAL for the
descriptor heaps) would then fail allocation on any device without a
host-visible device-local heap (no resizable BAR).

It now takes a `preferred` mask distinct from `required`: a type
satisfying both is chosen first, falling back to a required-only match
when the preference is unavailable, and throwing only when even
`required` cannot be met. VulkanBuffer::Create/Resize gain an optional
trailing `preferredPropertyFlags`, and the descriptor heaps now treat
DEVICE_LOCAL as a preference on top of mandatory HOST_VISIBLE.

This does not touch any flush/barrier behaviour — coherency is not
assumed anywhere here.

Adds tests/MemoryTypeFallback, a pure-CPU test that installs synthetic
memory layouts and exercises selection, preference, fallback, and the
unsatisfiable-required throw.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

interfaces/Crafter.Graphics-Device.cppm

@@ -199,7 +199,12 @@ export namespace Crafter {
         // ComputeShader read the offset off the pipeline they record.
 
         static void CheckVkResult(VkResult result);
-        static std::uint32_t GetMemoryType(std::uint32_t typeBits, VkMemoryPropertyFlags properties);
+        // Selects a memory type index from typeBits that satisfies `required`.
+        // When `preferred` bits are also given, a type satisfying both is
+        // chosen first; if none exists we fall back to required-only rather
+        // than throwing. Throws only when even `required` cannot be met (no
+        // valid memory exists for the allocation).
+        static std::uint32_t GetMemoryType(std::uint32_t typeBits, VkMemoryPropertyFlags required, VkMemoryPropertyFlags preferred = 0);
 
         // ─── Wayland key repeat ────────────────────────────────────────
         // TickKeyRepeats fires onRawKeyDown / onRawKeyHold / onTextInput on