[Bug] Sampler Bug: last_logits statically assigned to an int index

[drewjin]

In the implementation of the sampler of Fast-dLLM-v2 and Dream, shifted last logits are mistakenly assigned as an int index:

https://github.com/zhijie-group/Diffulex/blob/fast_dllm_v2/diffulex/sampler/fast_dllm_v2.py#L17

https://github.com/zhijie-group/Diffulex/blob/fast_dllm_v2/diffulex/sampler/dream.py#L16

[drewjin]

Fixed with #8