[Model][SM70] Accept DFlash embed replica across split load_weights c…

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AutoWeightsLoader groups consecutive tensors by top-level prefix, so a checkpoint whose shard order interleaves model.language_model.* with lm_head/model.visual.* (the 33-shard nvidia/GLM-5.3-Flash-NVFP4 layout) calls Glm5NextModel.load_weights more than once on the final pipeline stage. The DFlash target-embedding replica check assumed a single call and raised on the group without embed_tokens.weight. Record the replica as loaded when any call delivers it; spec_decode/dflash/utils.py still refuses to borrow an unloaded replica.

Claude-Session: https://claude.ai/code/session_015W5aeeDsFXgtoDWJZjtDpZ

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