fix(panels): enforce fixed-length array for color theme values

Change color theme type from variable-length list to fixed-length array of 3 floats,
ensuring correct RGB color value representation in RON format

modules/panels.nix

@@ -86,7 +86,7 @@ in
                 "Dark"
                 "Light"
                 "ThemeDefault"
-              ]) (ronTupleEnumOf (listOf float) [ "Color" ]);
+              ]) (ronTupleEnumOf (ronArrayOf float 3) [ "Color" ]);
             example = {
               __type = "enum";
               variant = "Dark";