[training] fix: Add cu_seqlens_argmin to vlm packed sequence#2246

ko3n1g merged 8 commits intomainNVIDIA-NeMo/Megatron-Bridge:mainfrom

chcui/fix_vlm_packed_sequenceNVIDIA-NeMo/Megatron-Bridge:chcui/fix_vlm_packed_sequenceCopy head branch name to clipboard