feat(ascend): add disk checkpoint NPU patches

[wangx700]

Adds only the disk checkpoint serving patches required by the PR-413 NPU stack.

• Append the validated vLLM disk checkpoint loader patch.
• Append NPUWorker.pull_weights() for Ascend collective RPC.
• Validated with git apply --check --whitespace=nowarn against pinned vLLM e6bfe03 and vLLM-Ascend fd815467 from [NPU] Sync Ascend with main and consolidate NPU adaptations vllm-project/vime#413.

8-card disk validation

Validated on Ascend NPUs 8-15 with Qwen3-4B, disk transport, num_rollout=10, rollout batch size 4, two samples per prompt, and response length 256. The table excludes the final v10 update because it overlaps Ray/vLLM job teardown; it compares the initial sync and stable v1-v9 updates.

Stage	Delta ratio	Delta wire	Delta update	Delta E2E	Full ratio	Full checkpoint	Full update	Full E2E
Initial sync	-	-	5.64s	34.05s	-	-	6.13s	48.41s
v1	0.56%	0.13 GB	10.19s	28.45s	100%	7.49 GiB	6.59s	31.09s
v2	0.63%	0.14 GB	4.67s	21.66s	100%	7.49 GiB	6.41s	30.36s
v3	0.70%	0.15 GB	4.24s	20.49s	100%	7.49 GiB	7.26s	31.12s
v4	0.60%	0.13 GB	4.98s	28.05s	100%	7.49 GiB	5.83s	26.13s
v5	0.84%	0.17 GB	4.17s	20.98s	100%	7.49 GiB	6.91s	25.66s
v6	0.63%	0.14 GB	4.23s	20.89s	100%	7.49 GiB	6.12s	26.96s
v7	0.61%	0.13 GB	4.34s	21.32s	100%	7.49 GiB	6.59s	28.42s
v8	0.58%	0.13 GB	4.16s	21.11s	100%	7.49 GiB	6.79s	29.80s
v9	0.77%	0.16 GB	4.30s	21.54s	100%	7.49 GiB	6.38s	29.86s
v1-v9 mean	0.66%	~0.14 GB	5.03s	-	100%	7.49 GiB	6.54s	-
10 rollout steps	-	-	-	238.55s	-	-	-	307.81s

E2E uses perf/step_time and covers rollout, training wait, training, and the update attributed to the step. Delta transfers about 0.66% of the model on average, but vLLM still reloads a reconstructed 7.49 GiB safetensors checkpoint on this NPU path.