Support variable-size anchored overworld sprites

src/mods/Schemas.lua

@@ -592,6 +592,13 @@ R.sprites = {
     image = f.path,
     frames = f.int(1),
     walker = f.opt(f.bool),
+    -- Optional sheet geometry for mod actors.  Defaults match the vanilla
+    -- 16x16 grounded walker; anchors are measured from each frame's
+    -- top-left in pixels (default: bottom-center).
+    frameWidth = f.opt(f.int(1)),
+    frameHeight = f.opt(f.int(1)),
+    anchorX = f.opt(f.num),
+    anchorY = f.opt(f.num),
     trueColor = f.opt(f.bool),
     -- Mod art can opt into an existing ROM sprite's Advanced-mode OBJ
     -- palette assignment without claiming that the image itself came from