Refraction samples are clamped to the layer rectangle instead of the buffer, so a sample past the
layer's edge in a buffer with transparent padding (a half-resolution preview's, a text or shape
layer's) repeats the layer's edge pixels rather than reaching the pale colour that stands in for
transparent ones. Transparent pixels inside the layer still show it. Same bounds on the GPU path.
Re-pins the four half-resolution CC Bubbles golden hashes (aarch64 macOS); the full-resolution
ones are unchanged. Adds a CPU test and a GPU-vs-CPU parity test on padded buffers.
Near the borders a bubble's refraction (liquid) or reflection (metal) sample
lands outside the layer. sample_bilinear returns transparent there, so the
pale stand-in colour for transparent pixels showed through, a band of washed-out
bubbles along every edge. Sample with edge pixels repeated instead, on the CPU
and in the GPU kernel; the pale colour stays for genuinely transparent pixels.
The CC Bubbles golden hashes are re-pinned (the half-resolution cases pad the
buffer with transparent pixels and are unchanged).