Clarify installer paths and backup locations

README.md

@@ -62,7 +62,7 @@ cd Lumen-wallpaper
 
 To enable it manually, open **System Settings → Wallpaper**, select **Lumen Wallpaper**, and click Apply. The Vulkan environment is loaded for new Plasma sessions from `~/.config/plasma-workspace/env/lumen-vulkan.sh`; log out and back in if necessary.
 
-To return to the previous wallpaper, select it in the same settings page. Activation backups are kept outside the source package in the build directory.
+To return to the previous wallpaper, select it in the same settings page. Activation backups are stored in `PREFIX/share/lumen-wallpaper/` when installed through the installer, or in the source build directory when `activate.sh` is called directly. `LUMEN_STATE_DIR` overrides this location.
 
 ## Custom shaders
 

scripts/install.sh

@@ -23,7 +23,7 @@ Options:
 
 Environment:
   PREFIX          Installation prefix (default: ~/.local)
-  BUILD_DIR       Build directory (default: ./build)
+  BUILD_DIR       Build directory (default: <source>/build)
   LUMEN_STATE_DIR Activation backups and logs (default: PREFIX/share/lumen-wallpaper)
 EOF
 }