build!: convert :rsdroid to a java-library: anki-backend-core - #770

Node.js 20 is deprecated. The following actions target Node.js 20 but are being forced to run on Node.js 24: mikehardy/runner-fallback-action@v1. For more information see: https://github.blog/changelog/2025-09-19-deprecation-of-node-20-on-github-actions-runners/

using runner: macos-26

Original error: Error: Input required and not supplied: github-token

Checking for available runners failed, but fallback-on-error is true