model: add DSpark support for Nemotron3.5

[ruixiang63]

Overview

Support DSpark model for Nemotron3.5-lightning NVFP4: https://huggingface.co/nvidia/NVIDIA-Nemotron-3.5-Lightning-30B-A3B-NVFP4-DSpark

Performance results: (Tested with NVIDIA-Nemotron-3.5-Lightning-30B-A3B-UD-Q4_K_M.gguf on NVIDIA L40S)

Comparison: baseline=speed-bench-qualitative-nemotron.json speculative=speed-bench-qualitative-nemotron-dspark.json
category       base_avg_pred_t/s  spec_avg_pred_t/s  decode_speedup  base_avg_latency  spec_avg_latency  latency_speedup  accept_rate
-------------  -----------------  -----------------  --------------  ----------------  ----------------  ---------------  -----------
coding         165.48             214.77             1.30x           3.337s            2.925s            1.14x            0.4431     
humanities     165.16             202.66             1.23x           4.943s            4.286s            1.15x            0.3731     
math           164.42             221.93             1.35x           3.220s            2.403s            1.34x            0.4621     
qa             164.70             188.28             1.14x           3.244s            2.892s            1.12x            0.3553     
rag            165.12             244.60             1.48x           5.019s            3.847s            1.30x            0.5454     
reasoning      164.99             222.26             1.35x           3.228s            2.443s            1.32x            0.4621     
stem           164.82             220.01             1.33x           3.150s            2.375s            1.33x            0.4621     
writing        163.94             186.67             1.14x           3.400s            3.111s            1.09x            0.3620     
multilingual   164.76             235.47             1.43x           3.285s            2.424s            1.35x            0.4849     
summarization  165.49             221.08             1.34x           3.182s            2.527s            1.26x            0.4626     
roleplay       165.25             224.46             1.36x           8.268s            6.387s            1.29x            0.4742     
overall        164.92             216.56             1.31x           4.025s            3.238s            1.24x            0.4432  

Additional information

Requirements

• I have read and agree with the contributing guidelines
• AI usage disclosure: Yes, paired with Cursor

[ruixiang63]

@ggerganov needs one more approval.

[ruixiang63]

Thanks @ngxson for resolving the conflicts. Merging this PR.