fix dllm mask on set_step

[grimoire]

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Modification

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[Copilot]

Pull request overview

This PR fixes the DLLM (Disaggregated Large Language Model) mask handling in the set_step method. The change modifies how mask values are updated when the sequence step boundary is reset.

Changes:

• Modified the set_step method in SchedulerSequenceDLLM to change only DLLM_CACHED values to DLLM_UNMASKED instead of setting all values in the range to DLLM_MASKED

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[Copilot]

The slice should use start:end instead of start:. The variable end is calculated on line 201 but is not used in the new code. This causes the mask update to incorrectly affect elements beyond num_history_ids, potentially modifying mask values that should remain unchanged.

Suggested change

	to_change_mask = self.history_dllm_mask[start:]
	to_change_mask = self.history_dllm_mask[start:end]

[RunningLeon]

LGTM