As in PhotoCraft: when portable.txt (or LightCraft.portable) sits next to the
executable, config_dir() is <exe dir>/LightCraftData, so settings, logs and
models stay with a portable copy instead of %APPDATA%. LIGHTCRAFT_CONFIG_DIR
still wins and is used without probing beside the executable. A portable
folder that can't be written logs a warning and the platform folder is used.
The check runs once per process.
Co-Authored-By: Claude Opus 5.5 <[email protected]>
