Add-ons: Parametric Shape Tool — re-editable stars, polygons, rings, arrows, gears and more

Path Precision Tools gains the Parametric Shape Tool: ten kinds of shape
(rectangle, ellipse, polygon, star, ring, arrow, cross, heart, gear,
speech bubble) that stay editable as numbers.

- Geometry in vectorcraft_pathops::addons::pathtools::shapes: each kind's
  outline, corner rounding limited to the middle of a side, a fingerprint
  of the outline, recovery of centre, size and rotation after a move,
  turn or scale, and recognition of plain rectangles, ellipses and
  regular polygons.
- The tool (parametricShape, All Tools drawer and Object › Plug-ins ›
  Path Precision Tools only, no shortcut): drag from the centre (Shift:
  45° steps), arrow keys change the count and values while dragging,
  handles edit a selected shape, double-click places one.
- Commands addon.pathtools.shape.create / .set / .convert, one undo step
  each; params checked (counts 3..1000, sizes up to 16384 pt).
- A shape keeps its numbers in one object-data entry (vc-pathtools-shape)
  that SVG export already leaves out; anchor edits make it a plain path.
- Parametric Shape panel, cursor stand-in, catalog rows in all 25
  languages, docs and tests.

crates/pathops/src/addons/pathtools.rs

@@ -1,10 +1,11 @@
 //! Path Precision Tools' geometry: anchor edits for the Anchor Inspector (smooth by the auto-smooth
 //! rule, equalise handles, add evenly spaced anchors, close), the readouts the Measure & Inspect
 //! tool shows over a path, open paths lengthened or shortened at an end ([`extend`]) and the places
-//! where paths cross ([`crossings`]).
+//! where paths cross ([`crossings`]), and the Parametric Shape Tool's shapes ([`shapes`]).
 
 mod crossings;
 mod extend;
+pub mod shapes;
 #[cfg(test)]
 mod tests;