MT RTS - EXTERNAL HERO AVATARS

Editor path: <UnityProject>/ExternalData/Portraits/Heroes/
Build path : <folder containing MT_RTS.exe>/ExternalData/Portraits/Heroes/

Canonical naming: hero_###_<hero_code>.png
Example: hero_005_cao_cao.png

The hero database field externalPortraitFile stores the relative path.
If an image exists, the game loads it. If missing/corrupt, gameplay continues and uses the existing Resources/atlas fallback.
Images remain outside Assets and are not required for the game to run. The Editor build hook copies ExternalData beside a successful desktop build.
