gui_toolkit 0.42.3

Fixed

• CI: green again and about 6 minutes instead of 30 to 37. The CHANGELOG step failed on every push (tools/changelog_test.ps1 ended with the exit code of a command it made fail on purpose; it now exits 0); a test package of a single test counted as failed (text_backends printed "The test was successful", not "All tests were successful"; both are accepted now). The jobs run in parallel: build (changelog, examples, shaders), the windowless tests (tools/test_windowless.ps1, the step's script moved there) and the WebGPU tests in four groups (tools/test_backends.ps1 -Group ci1..ci4, checked to hold every package once; -Group sample on pull requests) with DXC, a third of the time of FXC on WARP (FXC still runs two packages, -Define TOOLKIT_WGPU_DX12_COMPILER=fxc); each job and slow step has a timeout; the Rust libraries, naga's translator, the emoji font and DXC are cached; Odin is set up by .github/actions/setup-odin, its archive hashed with .NET rather than Get-FileHash. Every push to master keeps its own run (only pull requests cancel the previous one).
• WebGPU: render.video_convert converts pictures in memory (I420, NV12; P010 and 10-bit I420 when the adapter has TextureFormat16bitNorm) with video.wgsl, crop, rotation, matrix and range included, as on Direct3D 11: it returned false for every picture (render/wgpu_video.odin). A decoder's Direct3D 11 texture (gpu_texture) is still refused on WebGPU (wgpu-native cannot import it); tests/video checks that refusal there instead of calling a Direct3D 11 device the backend does not have (it crashed).
• WebGPU: Slug text when the device refuses its shaders draws nothing instead of passing a missing shader module to the pipeline: r.slug.failed is honoured by both backends (it was Direct3D 11 only), a refused slug.wgsl sets it, a recreated device asks again.