Discover facial features from asset directories

art/exported/characters/faces/README.md

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+# Drop-in facial features
+
+Facial feature textures are discovered when the game starts. Put new PNGs in
+the matching directory, restart the game, and the option will appear in the
+Profile customization page.
+
+```text
+eyes/<id>.png
+noses/<id>.png
+mouth/<id>.png
+```
+
+The category directory is authoritative. A category prefix is optional, so
+both `sleepy.png` and `eyes_sleepy.png` become the option ID `sleepy`.
+Filenames are normalized to lowercase snake_case. Use stable names because
+the resulting IDs are stored in appearance snapshots and sent to peers.
+
+Keep each PNG on the established facial-feature canvas with an RGBA
+transparent background. Godot imports the PNG automatically in the editor;
+the runtime registry ignores `.import` files and other non-PNG files.
+
+The current game bundles its facial assets under `res://`. Adding a file to a
+development checkout is picked up on the next startup. An exported build must
+be rebuilt to include newly added `res://` files in its package.