Python, WASM variants, the playground and GPU compute in one day

The experimental Python 3 frontend lands, compiling to the same register bytecode as JavaScript, together with WASM build variants, a folder-based playground, GPU graphs from Python and a Torch subset with GPU training.

378b18de adds the Python frontend, the javascript and all WebAssembly variants and the playground. 5fd22bcb is titled "Python: Zipp's own full-language implementation": the RustPython parser for the AST, Zipp's own symbol table and emitter to register bytecode, and a JavaScript-shaped runtime for the object model, validated byte for byte against CPython on a committed corpus.

8bb14918 integrates the GPU Lab so Python graphs can execute on WebGPU, WebGL2, compiled WASM kernels or JavaScript. 9651dd40 makes Python projects folders, adds the Torch subset and puts the lab in the playground. 955914f3 adds asynchronous dense GPU training through torch.compile(step, training=True) and pins down the virtual-filesystem change protocol. The docs are careful: a Python and Torch subset, not CPython or PyTorch.