- Implement 10 manual save slots with metadata (turn, year, empire, species, date)
- Add ☰ game menu button with Save, Load, Return to Main Menu, and Quit to Arcade
- Replace generic sounds with 7 custom Vega sound effects (select, build, close,
newturn, unit, view, warp)
- Introduce uiClick() helper to standardize click sound across all modal screens
- Update research video paths for umbrix and rrashaa species
- Refactor button handlers in all Vega screens to use uiClick() pattern
- Save/load uses scene restart via pendingSavedState for clean HUD/map teardown
