Port processing4 examples to Python.

[tychedelia]

There are some gaps that were surfaced from porting these, I'll follow up with fixing them. Then, we should be able to do a 1:1 screenshot comparison to make sure that we are rendering everything correctly.

[github-actions]

Visual regression: 1 changed of 43 cases

case	status	detail
py_flocking_gpu	❌ changed	5.8% of pixels differ

If these changes are intentional, add the deliberate-rendering-change label.

_{baseline 0b1a55dd20 · adapter llvmpipe (LLVM 20.1.2, 256 bits) (Vulkan, Mesa 25.2.8-0ubuntu0.24.04.4 (LLVM 20.1.2))}

Open the visual report · workflow run

[catilac]

merged!