qwen3_5 cuda: 2, 3, 5 and 6-bit tiles of their own width and a prompt GEMM for them (27B oQ2 on 16 GB) - #859

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, mlugg/setup-zig@v2. For more information see: https://github.blog/changelog/2025-09-19-deprecation-of-node-20-on-github-actions-runners/