Mpi Tiny Vae Loader

Loads a tiny TAEHV preview decoder that ComfyUI's own VAELoader cannot build. Core picks the decoder width from the latent channel count and has no case for a 24-channel latent with a 12-wide decoder, which is what MiniMax H3's taeh3 is — VAELoader raises a state-dict size mismatch on it. Anything core already handles is passed straight through to VAELoader's own code path, so this is a safe drop-in for any tiny decoder.