1.15.0 "Where everyone is": roadmap 29's finished core lanes (sessions R4-R6, SDK polish + undo, football suite, Dungeon Realms/Untangle templates, embed flag) - #228

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, actions/setup-node@v4. For more information see: https://github.blog/changelog/2025-09-19-deprecation-of-node-20-on-github-actions-runners/