FractalTokenizer: Adaptive Image Tokenization

Research code exploring image tokens allocated by estimated information. A one-seed v2 ImageNet100 run reached 75.02% top-1 at 128 tokens, below a 256-token grid baseline at 76.32%; a later modified-density rerun scored 73.52%. The deterministic v3 tokenizer has synthetic tests, but no completed matched-rate downstream result. A rate-distortion advantage has not been established.