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/pen_input.js

@@ -69,8 +69,8 @@ const focusSettleOn = !new URLSearchParams(location.search).has('no_focus_settle
  *     The pointer moves over the page with no button down and nothing in
  *     progress (a mouse, or a pen in the air above a tablet that reports
  *     it; a finger never hovers).
- * @property {() => void} [hoverEnded]
- *     The pointer left the page, or pressed.
+ * @property {(left?: boolean) => void} [hoverEnded]
+ *     The pointer pressed, or left the page (`left` true).
  * @property {(clientX: number, clientY: number) => boolean} [beginHold]
  *     The pointer has rested on the page for HOLD_MS, with any tool: a
  *     hold.  True if something under it took the hold (an image to move
@@ -367,7 +367,7 @@ export function attachPenInput(surface, target) {
   }
   surface.addEventListener('pointerup', finish);
   surface.addEventListener('pointercancel', finish);
-  surface.addEventListener('pointerleave', () => { if (activePointer === null) target.hoverEnded?.(); });
+  surface.addEventListener('pointerleave', () => { if (activePointer === null) target.hoverEnded?.(true); });
   surface.addEventListener('lostpointercapture', (event) => {
     if (event.pointerId === activePointer) trace(`capture of pointer ${event.pointerId} lost while active`);
   });