FlushDevice/FlushHost called vkFlushMappedMemoryRanges /
vkInvalidateMappedMemoryRanges unconditionally. Record the chosen
memory type's propertyFlags at Create time (via the index GetMemoryType
returns, not the requested flags) and early-return when HOST_COHERENT.
The cmd overload still always emits its pipeline barrier — only the
redundant host-side flush/invalidate is gated.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
