Support DSpark speculative decoding for DeepSeek-V4-Flash-0731 in sglang-kt

Reminder

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Description

Summary

DeepSeek-V4-Flash-0731 (official release, 2026-07-31) ships a new DSpark speculative decoding module instead of the NextN-style MTP head used in DeepSeek-V4-Flash-Preview. sglang-kt==0.6.4 only supports EAGLE/NEXTN speculative algorithms and cannot load the new draft head, forcing users to disable speculative decoding entirely (~2x decode speed loss).

Request: port DSPARK support to sglang-kt (upstream SGLang supports it since v0.5.16).

Background

Per the official release notes, DeepSeek-V4-Flash-0731 "has the same model structure as DeepSeek-V4-Flash-DSpark, i.e. it comes with a speculative decoding module attached."

The checkpoint layout changed:

• Preview: single NextN MTP layer with top-level keys model.enorm/hnorm/e_proj/h_proj (+ weight_scale_inv)
• 0731: three full MoE draft layers mtp.0, mtp.1, mtp.2 (4,705 mtp.* keys in model.safetensors.index.json), each containing attention + 256 routed experts + 1 shared expert, plus mtp.2.confidence_head.proj and mtp.2.markov_head.markov_w1/w2

New config.json fields:

"dspark_block_size": 5,
"dspark_noise_token_id": 128799,
"dspark_target_layer_ids": [40, 41, 42],
"dspark_markov_rank": 256

### Pull Request

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