Arranging: boxes on everything, handwriting movable, the Eraser's preview, a Circle shape, pixel-exact cues

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>

client/js/page_model.js

@@ -49,9 +49,9 @@ export const IMAGE_MARGIN = 50;
 
 /**
  * The shapes of the Shape tool (shapes.js), as a stroke records its kind.
- * @typedef {'rectangle' | 'ellipse' | 'line' | 'arrow'} ShapeKind
+ * @typedef {'rectangle' | 'circle' | 'ellipse' | 'line' | 'arrow'} ShapeKind
  */
-export const SHAPE_KINDS = /** @type {const} */ (['rectangle', 'ellipse', 'line', 'arrow']);
+export const SHAPE_KINDS = /** @type {const} */ (['rectangle', 'circle', 'ellipse', 'line', 'arrow']);
 
 /** Numbers per point in Stroke.points. */
 export const POINT_SIZE = 3;