feat(dspark): add Qwen3.5-4B draft config and managed-local NPU disaggregated recipe

[curnane-lab]

Motivation

Add a Qwen3.5-4B DSpark draft config and a recipe for the managed-local disaggregated stack on Ascend NPU, mirroring the DFlash recipe from #722.

Modifications

• configs/qwen3.5-4b-dspark.json: DSparkDraftModel config for Qwen3.5-4B (block_size 16, 5 draft layers on target layers [1, 8, 15, 22, 29], markov_rank 256, confidence head).
• examples/configs/qwen3.5-4b-dspark-disaggregated-npu.yaml: single-node managed-local recipe (Mooncake + capture server on device 0 + 14-rank trainer on devices 2-15; 8-card fallback in comments). DSpark loss weights ce/l1/confidence = 0.1/0.9/1.0, num_anchors: 186, sdpa.
• examples/README.md: register the recipe.

Note: beyond DFlash, DSpark also streams the target final hidden state (target_last_hidden_states) through the same capture sink; that path is exercised for the first time on Ascend here, so an A3 smoke run should precede merge.

Related Issues

Stacked on #722 (merge after it): the branch is main + the recipe commit + a merge of npu_disaggregated. The diff shrinks to the recipe alone once #722 lands. Incremental view: curnane-lab/SpecForge@npu_disaggregated...dspark_npu_disaggregated

Accuracy Test

NA (no model-side code modified)

Benchmark & Profiling

NA

Checklist

• Format your code according to the Code Formatting with Pre-Commit.
• Add unit tests as outlined in the Running Unit Tests.
• Update documentation / docstrings / example tutorials as needed, according to Writing Documentation.
• Provide throughput / latency benchmark results and accuracy evaluation results as needed, according to Benchmark and Profiling and Accuracy Results.
• For reviewers: If you haven't made any contributions to this PR and are only assisting with merging the main branch, please remove yourself as a co-author when merging the PR.
• Please feel free to join our Slack channel at https://sgl-fru7574.slack.com/archives/C09784E3EN6 to discuss your PR.

[gemini-code-assist]

Caution

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