Improve resolving render targets

[skallweitNV]

Both D3D12 and Vulkan require more work for resolving render targets after a render pass. Both currently just resolve the first subresource only, but the provided TextureViews can reference specific subresources.

[skallweitNV]

@claude can you implement this for D3D12 and Vulkan and add a unit test?

[github-actions]

Claude finished @skallweitNV's task —— View job • claude/issue-57-20250806-0922 • Create PR ➔

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I've successfully implemented improved render target resolving for D3D12 and Vulkan backends and added comprehensive unit tests! ✅

Todo List

• Analyze current render target resolving implementation in D3D12 and Vulkan
• Use deepwiki to understand architectural patterns for render target resolving
• Implement improved subresource resolving for D3D12 backend
• Implement improved subresource resolving for Vulkan backend (already correct)
• Create unit test to verify the functionality
• Build and test the changes
• Commit and push changes

Implementation Summary

D3D12 Backend (src/d3d12/d3d12-command.cpp)

• Fixed hardcoded subresource indices (0) in ResolveSubresource calls
• Now properly iterates through all mips and layers in the TextureView's subresource range
• Handles kAllMips and kAllLayers constants correctly
• Uses D3DUtil::getSubresourceIndex() to calculate correct subresource indices

Vulkan Backend

• Upon investigation, the implementation was already correct!
• The resolveImageView uses the TextureView's specific subresource range via getView().imageView
• This creates a Vulkan image view with the exact baseArrayLayer, layerCount, baseMipLevel, and levelCount from the TextureView descriptor

Unit Test (tests/test-resolve-resource-tests.cpp)

• Added ResolveResourceSubrange test that verifies resolving to specific array layers
• Creates textures with 2 array layers and resolves specifically to layer 1
• Verifies that layer 0 remains unaffected (black) while layer 1 contains rendered content
• Test passes on both D3D12 and Vulkan backends

Verification

All tests pass successfully:

• resolve-resource-simple: ✅ (existing functionality unchanged)
• resolve-resource-subrange: ✅ (new test for subresource-specific resolving)
• Build completes without errors or warnings