Extend sketch constraints toward FreeCAD parity, staying DWG-native-compatible

Arcs are now full constraint participants (center/radius via the existing
Circle-shaped solver path, plus real endpoints kept consistent by arc-rules
CurveValue constraints); adds Diameter/DistanceX/DistanceY/ArcLength/Normal
constraint kinds and initial Ellipse entity support (center-based
constraints only). DWG-native class mappings and gaps (ArcLength, Ellipse)
are grounded against real ObjectARX headers rather than guessed, so files
saved with DWG-native constraints stay honest about what AutoCAD can
actually represent.

Also fixes a case-sensitivity bug where a lowercase named-parameter
reference typed at a dimensional constraint's value prompt was rejected
(the command line uppercases SingleToken input before the parameter-name
lookup), and adds a "Used by" column to the Named Parameters panel.

Co-Authored-By: Claude Sonnet 5 <[email protected]>

src/app/commands/draw.rs

@@ -1000,7 +1000,7 @@ impl OpenCADStudio {
                 self.tabs[i].active_cmd = Some(Box::new(new_cmd));
             }
 
-            "PCONSTRAINT" | "QCONSTRAINT" | "ECONSTRAINT" | "TCONSTRAINT" | "LCONSTRAINT" => {
+            "PCONSTRAINT" | "QCONSTRAINT" | "ECONSTRAINT" | "TCONSTRAINT" | "LCONSTRAINT" | "NRCONSTRAINT" => {
                 let handles = self.tabs[i].scene.selected_handles_in_order();
                 if handles.is_empty() {
                     use crate::modules::draw::select::SelectObjectsCommand;
@@ -1019,6 +1019,7 @@ impl OpenCADStudio {
                         "QCONSTRAINT" => (ConstraintKind::Perpendicular, "Perpendicular constraint"),
                         "TCONSTRAINT" => (ConstraintKind::Tangent, "Tangent constraint"),
                         "LCONSTRAINT" => (ConstraintKind::Colinear, "Colinear constraint"),
+                        "NRCONSTRAINT" => (ConstraintKind::Normal, "Normal constraint"),
                         _ => (ConstraintKind::Equal, "Equal constraint"),
                     };
                     return Some(self.apply_cmd_result(CmdResult::AddSketchConstraint {

src/app/view/modal.rs

@@ -175,13 +175,15 @@ impl OpenCADStudio {
                 )
             }
             super::super::ModalKind::NamedParameters => {
+                let scene = &self.tabs[self.active_tab].scene;
                 sized_flow(
                     ex,
-                    620,
+                    820,
                     520,
                     |flow| {
                         crate::ui::window::named_parameters::view_window(
                             &self.named_parameter_editor_rows,
+                            scene,
                             flow,
                         )
                     },