Shape draw: dotted preview doesn't match the shape / pointer is offset from it

[vibhavkatre]

Reported by Vibhav (video QA, qa-2026-08-02-1732), ~03:37–04:14 (frame confirmed).

While drawing, the dotted guidance is wrong/offset: a rectangle preview looks like a rounded rectangle, and for an ellipse the pointer sits away from the dashed circle (confirmed in frame — cursor is bottom-right of the circle). Make the preview match the shape and keep the pointer on the shape consistently.

Where to look: block draw/preview interaction + composables/useShapeCreation.js.