Fixed

• Software backend offscreen textures — split deviceReady from gpuReady in GPU shared state. On rasterAtlas strategy (software adapter), device is alive for texture/buffer operations while shape pipelines (SDF/stencil/convex) are skipped. CreateOffscreenTexture now checks deviceReady instead of gpuReady. ensurePipelines() skips shape pipelines on rasterAtlas to prevent SPIR-V hang. Follows Skia Graphite kRasterAtlas pattern.

• GPU tests hardcoded MSAA sampleCount=4 — 48 test sites replaced with testSampleCount(t, device) probe that delegates to production resolveSampleCount (Skia Graphite pattern). Tests now pass on software backends (llvmpipe, SwiftShader) that only support sampleCount=1.

Added

• Software offscreen upload — uploadPixmapToView() uploads CPU-rasterized pixmap to offscreen GPU texture via Queue.WriteTexture on rasterAtlas strategy. RGBA→BGRA swizzle. CopyDst usage on offscreen textures.

• SurfacePixelWriter zero-copy path — duck-typed interface in ggcanvas.Render(). On software backend, writes pixmap directly to surface framebuffer via wgpu.Surface.PresentPixels (single memcpy+swizzle, no render pass). Damage rects forwarded before present.

Changed

• Dependencies: wgpu v0.30.10 → v0.30.19, gogpu v0.44.1 → v0.44.6, gpucontext v0.21.0 → v0.21.1, goffi v0.5.6 → v0.6.0, golang.org/x/image v0.43.0 → v0.44.0, golang.org/x/text v0.39.0 → v0.40.0, golang.org/x/sys v0.46.0 → v0.47.0.