feat(api): abort signal support for vscode-lm (completePrompt + createMessage) - #1300

Node.js 20 is deprecated. The following actions target Node.js 20 but are being forced to run on Node.js 24: actions/checkout@34e114876b0b11c390a56381ad16ebd13914f8d5, github/codeql-action/analyze@411c4c9a36b3fca4d674f06b6396b2c6d23522c6, github/codeql-action/init@411c4c9a36b3fca4d674f06b6396b2c6d23522c6. For more information see: https://github.blog/changelog/2025-09-19-deprecation-of-node-20-on-github-actions-runners/