Vulkan: add standalone renderer foundation

[r0shn1ch]

Summary

• Add a standalone xrRenderVK foundation with device selection, swapchain frames, resize recovery, DDS upload, and image state tracking.
• Add a Vulkan screen-copy shader pair, generated SPIR-V 1.0, and a DXC regeneration script.
• Add ScreenCopyPass: separate image/sampler descriptors, a graphics pipeline, and a fullscreen draw callback.

This is a direct Vulkan path. Gameplay still uses the existing OpenGL renderer; no Vulkan gameplay integration or device smoke test is included.

Roadmap

1. Frame and texture foundation — in place.
2. Swapchain resize recovery — in place.
3. Screen-copy shaders and shader modules — in place.
4. Screen-copy descriptors, pipeline, and frame callback — in place.
5. Connect engine images, then render UI and static geometry through Vulkan.
6. Port models, terrain, particles, deferred lighting, shadows, and post-processing.
7. Add surface-loss and Android, Windows, and Linux lifecycle support; validate levels and mods.
8. Profile both renderers and select Vulkan for gameplay after feature parity.

Validation

• All xrRenderVK sources compile as C++17 with -Wall -Wextra -Werror (-Wno-missing-field-initializers for Vulkan aggregates).
• The frame and screen-copy sources compile together as one unity translation unit.
• Host tests pass for DDS decoding, image state tracking, shader modules, and the screen-copy pass.
• DXC compiles both shaders; SPIR-V 1.0 headers and fragment descriptor bindings 0 and 1 were checked.
• Fork push Build: all 56 jobs passed. Push StyleCheck (clang-format, encoding, spacing) passed.
• No gameplay or GPU-device smoke test yet.

[Xottab-DUTY]

We already have a new NVRHI based renderer in development. It supports DX11, DX12 and Vulkan.
Check yohji/feat/framegraph branch.

[IriaSomobu]

+60k LOC :omg: