Fix MGE playthrough behavior and UI regressions

[wan0net]

Summary

• restore research discovery, first-contact diplomacy, production repeat, and MGE spaceship flow
• correct city, advisor, modal, video, audio, replay, option, and cheat interactions
• make the tribe selector fit an original 800-pixel desktop
• retain the intentional arrow-key viewport controls

Verification

• public runtime allow-list passed
• production build passed
• 270/270 Playwright tests passed
• live 800px playthrough checked through world setup, city founding, city screen, production selection, and advisors