chore: remove unused GSD agent scaffolding and its dangling references - #232

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

'err' is defined but never used

'err' is defined but never used

'gapListBefore' is assigned a value but never used

'e' is defined but never used

'getModelPath' is defined but never used

'USE_NEW_PROXY' is assigned a value but never used

'result' is assigned a value but never used

'e' is defined but never used

'listMediaViaWorkspaceLs' is defined but never used