Close the 0.9.3 UI polish milestone

Add deterministic captures 14-21 for the remaining screen-design states, fix the panel/button layout issues they exposed, and record 21/21 compare and judge results. Bump the source to 0.9.3 and move the completed milestone to DONE.md.

tools/check_screenshots.sh

@@ -18,5 +18,6 @@ if [[ -z "${DISPLAY:-}" ]]; then
 fi
 
 "${RUN[@]}" "$GODOT" --path . --script res://src/test/capture_screenshots.gd -- --out=res://docs/screenshots
+"${RUN[@]}" "$GODOT" --path . --script res://src/test/capture_ui_states.gd -- --out=res://docs/screenshots
 "${RUN[@]}" "$GODOT" --path . --script res://src/test/capture_prop_gallery.gd -- --out=res://docs/screenshots
 python3 tools/screen_designs.py compare