- Add TA-specific sound effects (machinegun, 50cal, rocket variants, unit/vehicle loss)
- Add background artwork and update core-units sprite sheet with correct path and dimensions
- Introduce pintle gun weapon with burst fire mechanics
- Switch weapon sounds to TA-themed audio; support sound arrays for random variant picking
- Add impactSound field to projectile weapons, propagated through sim events
- Reduce unit build times and increase structure HP for better pacing
- Enable idle breathing/rotation animations on resource generators
- Replace solid-color backdrop with painted background image on main menu
- Fix camera state cleanup so menus render correctly after gameplay
