[Scheduler] Charge the host-hit Mamba node slot in prefill admission - #43138

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

Summary report available at: https://github.com/sgl-project/sglang/actions/runs/37814326793#summary-113438924461