Rounded Rectangle sketch tool (#891) (#948)

* Rounded Rectangle sketch tool (#891)

A new SKETCH > CREATE command, sketch.rectangle.rounded, in the Rectangle
family: two opposite corners and a corner radius make a 2-point rectangle
whose four corners are filleted alike, as one undo step. The radius is one
parameter (one radius dimension, the other arcs equal to it), so changing it
changes all four corners. While drawing, Width, Height and Radius boxes take
typed values; typed width and height dimension the overall size between
opposite sides. Without a typed radius the corners get a fifth of the shorter
side.

Fixes #891

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

* Rounded Rectangle in the Simplified Chinese catalog

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

---------

Co-authored-by: Claude Opus 5.5 <noreply@anthropic.com>

crates/engine/src/cmd/sketch_dimensioned.rs

@@ -12,7 +12,9 @@ pub(super) fn draw(s: &mut Session, p: &Value) -> Result<Value> {
     let create = str_(p, "command").ok_or_else(|| bad(cmd, "`command` must name a supported sketch creator"))?;
     let roles: &[&str] = match create {
         "sketch.line" => &["length", "angle"],
-        "sketch.rectangle.two_point" | "sketch.rectangle.center" | "sketch.rectangle.three_point" => &["width", "height"],
+        "sketch.rectangle.two_point" | "sketch.rectangle.center" | "sketch.rectangle.three_point" | "sketch.rectangle.rounded" => {
+            &["width", "height"]
+        }
         "sketch.circle.center" | "sketch.circle.two_point" | "sketch.circle.three_point" => &["radius", "diameter"],
         "sketch.arc.center_point" => &["radius", "sweep"],
         "sketch.slot.center_to_center" | "sketch.slot.overall" => &["length", "width"],
@@ -82,6 +84,13 @@ pub(super) fn draw(s: &mut Session, p: &Value) -> Result<Value> {
         let (entities, ty) = match (create, role.as_str()) {
             ("sketch.line", "length") => (vec![curve(0)?], "length"),
             ("sketch.line", "angle") => (vec![curve(0)?], "angle"),
+            // A rounded rectangle's sides stop at the arcs: its size is between opposite sides.
+            ("sketch.rectangle.rounded", "width" | "height") => {
+                let [a, b] = if role == "width" { ["left", "right"] } else { ["bottom", "top"] };
+                let side =
+                    |k: &str| out["sides"].get(k).filter(|v| v.is_string()).cloned().ok_or_else(|| bad(cmd, "creator did not return its sides"));
+                (vec![side(a)?, side(b)?], "distance")
+            }
             (c, "width" | "height") if c.starts_with("sketch.rectangle.") => (vec![curve(usize::from(role == "height"))?], "length"),
             (c, "radius" | "diameter") if c.starts_with("sketch.circle.") => (vec![curve(0)?], role.as_str()),
             ("sketch.arc.center_point", "radius" | "sweep") => (vec![curve(0)?], role.as_str()),