refactor: remove unreachable starter-app shell — dead code, verified against the PR 1 test net - #925

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, actions/setup-node@49933ea5288caeca8642d1e84afbd3f7d6820020, actions/upload-artifact@b4b15b8c7c6ac21ea08fcf65892d2ee8f75cf882. For more information see: https://github.blog/changelog/2025-09-19-deprecation-of-node-20-on-github-actions-runners/