End2End-Diffusion

Set up and verify the nanogen development environment. Use when onboarding a new developer, after cloning the repo, when `uv sync` fails, when dependencies are broken, or when the user asks to install/fix/reset the environment. Triggers on "setup nanogen", "install dependencies", "uv sync failing", "fix environment", "fresh install", "verify setup".

Add a new HuggingFace-supported VAE to the stage1 tokenizer pipeline. Use when integrating a new VAE model from diffusers, adding autoencoder support, or the user says "add vae", "new vae", "integrate vae", "add autoencoder", "support X VAE".