Improve macOS stability, UI, camera, and terrain performance

[mehmetbat]

Summary

• fix missing infantry rendering on the native macOS/DXVK path
• stabilize Extras/options UI and persist camera preferences
• reduce terrain rebuild work after foundation height changes by batching bounded partial updates
• hoist invariant terrain-light calculations out of hot vertex loops

Compatibility

• renderer/client-side changes only; no AI or gameplay balance changes
• no save or replay format changes
• built and verified as a native Apple Silicon arm64 executable

Verification

• 8 source QA tests passed
• full macOS ARM64 z_generals build passed
• ad-hoc code-sign verification passed
• runtime tested successfully on an M1 Pro Mac

Notes

The terrain optimization was adapted from the GPLv3 CnCGeneralsZH-Reborn work while preserving this repository’s architecture and macOS renderer.

[mehmetbat]

Runtime validation update (Apple M1 Pro): the recommended quality/performance preset for a 1920x1200 external display is windowed 1920x1080:

./run.sh -win -xres 1920 -yres 1080

The same value can be persisted in the user Options.ini as Resolution = 1920 1080. Keep skirmish Game Speed at 30 for the original simulation pace and lowest background load.