Docs: Add A3 Docker image guidance for Atlas A3 machines

[hu-qi]

Fixes #3386

• Update Qwen3-30B-A3B.md to use A3-specific image tag
• Update Qwen3-Dense.md to provide both A2 and A3 image options
• Update Qwen3-Next.md to use A3-specific image for Atlas A3 environments

Previously, documentation only mentioned A2 images (vllm-ascend:version) but Atlas A3 machines require A3-specific images (vllm-ascend:version-a3). This change ensures users select the correct image for their hardware.

🤖 Generated with Claude Code

• vLLM version: release/v0.13.0
• vLLM main: vllm-project/vllm@ad32e3e

[gemini-code-assist]

Code Review

This pull request updates documentation across three files to add Docker image guidance for Atlas A3 machines. While the intent is to help users select the correct image, the changes in Qwen3-Dense.md and Qwen3-Next.md default to the A3-specific image. Since these tutorials appear to target both A2 and A3 users, this default could be misleading and cause issues for A2 users. I've suggested changes to make the selection explicit by commenting out both image options and instructing users to choose the one appropriate for their hardware. This should improve clarity and prevent configuration errors.

[github-actions]

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[Yikun]

Have you check all doc to include a3 part? otherwise LGTM