[S3-001] Establish the Gold Edition fidelity specification

Accidental duplicate of https://github.com/stacksjs/the-settlers-iii-remake/issues/17, created on 2026-10-22 when an interrupted roadmap publish (the disk filled during the run) could not see the existing issues. Closed without work; track S3-001 in https://github.com/stacksjs/the-settlers-iii-remake/issues/17.