Release v0.6.52: add Arc tool to screenshot editor

README.md

@@ -202,6 +202,10 @@ snapping and shape constraints are unchanged.
 Both drawn and recognized triangles have three independent vertex handles instead of bounding-box
 resize handles. Drag any vertex to reshape the triangle while keeping the other two fixed, even
 after rotation. Vertex edits support undo/redo, and the rotation and thickness handles remain available.
+**Arc (U)** draws an open half ellipse inside the dragged rectangle. Use the corner handles
+to resize it and the round handle to rotate it (Shift snaps to 15 degrees). Arcs support
+color, thickness, line style, moving, cloning, undo/redo and PNG export.
+
 **Trapezoid (B)** on the toolbar creates a trapezoid with parallel bases. Pencil recognition also
 fits nearly parallel, unequal bases into a clean trapezoid. Trapezoids support bounding-box resizing,
 rotation, styling and undo/redo; Ctrl+Z after recognition restores the original pencil stroke.