[Doc] cookbook: Refresh SemiAnalysis AgentX launches for Qwen3.5 and DeepSeek-V4.1-Flash GB300 - #44712

Node.js 20 is deprecated. The following actions target Node.js 20 but are being forced to run on Node.js 24: actions/checkout@v4, dorny/paths-filter@v3. For more information see: https://github.blog/changelog/2025-09-19-deprecation-of-node-20-on-github-actions-runners/

PR is missing the 'run-ci' label; skipping sgl-router tiers. Apply the label to opt in.