fix(converter): use vkGetDescriptorEXT for descriptor buffer population

[porkloin]

#11 seems to have introduced a regression that causes me to get a completely green video channel when streaming via moonshine HEAD. It looks like it was caused by ColorConverter shader was reading uninitialized descriptors. As far as I can tell, I think we need to use vkGetDescriptorEXT instead.

Tested on 9070XT with HEAD/main from moonshine, with git bisect on pixelforge and it looks like #11 definitely introduced it and this PR fixes it, but an extra set of eyes and test on non-AMD hardware would be appreciated.

[Copilot]

Pull request overview

Fixes a descriptor-buffer regression introduced after updating ash (#11) where the converter’s compute shader could read invalid/uninitialized descriptor data (observed as a constant-green output channel when streaming), by switching descriptor population to Vulkan’s runtime descriptor writer API.

Changes:

• Populate descriptor-buffer contents via vkGetDescriptorEXT (ash::ext::descriptor_buffer::Device::get_descriptor) instead of vkGet*OpaqueCaptureDescriptorDataEXT.
• Use the correct runtime descriptor sizes (*_descriptor_size) from VkPhysicalDeviceDescriptorBufferPropertiesEXT.
• Track the output buffer’s size and device address to build a VkDescriptorAddressInfoEXT for the STORAGE_BUFFER binding.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 3 comments.

File	Description
src/converter/pipeline.rs	Adds output buffer device-address usage/address tracking and switches to runtime descriptor-size queries.
src/converter/mod.rs	Replaces opaque capture descriptor flow with per-frame vkGetDescriptorEXT writes into the mapped descriptor buffer.

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[hgaiser]

Thanks! I didn't test this yet in Moonshine. I used the verify_all example, which interestingly did work fine.