feat(modify): EXTRIM — cookie-cutter trim on one side of a boundary (#253)

Run EXTRIM, pick a cutting boundary (line/arc/circle/ellipse/spline/
polyline), then click a side: every object crossing the boundary is
trimmed on that side and objects wholly on it are erased. Side is decided
by a parity crossing count (a segment to the pick point crossing the
boundary an even number of times is on the pick side), reusing the trim
intersection machinery; line boundaries extend to infinity. Line/arc/
circle are trimmed exactly; polyline/ellipse/spline via dense sampling.

Live preview while choosing the side: boundary in yellow, surviving parts
in blue, the removed parts in red.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

src/app/commands/dim.rs

@@ -914,6 +914,22 @@ impl OpenCADStudio {
                 self.tabs[i].active_cmd = Some(Box::new(new_cmd));
             }
 
+            "EXTRIM" => {
+                use crate::modules::draw::modify::trim::ExtrimCommand;
+                let all: Vec<_> = self.tabs[i]
+                    .scene
+                    .entity_wires()
+                    .iter()
+                    .filter_map(|w| {
+                        let h = Scene::handle_from_wire_name(&w.name)?;
+                        self.tabs[i].scene.document.get_entity(h).cloned().map(|e| (h, e))
+                    })
+                    .collect();
+                let new_cmd = ExtrimCommand::new(all);
+                self.command_line.push_info(&new_cmd.prompt());
+                self.tabs[i].active_cmd = Some(Box::new(new_cmd));
+            }
+
             "EXTEND" | "EX" => {
                 use crate::modules::draw::modify::trim::ExtendCommand;
                 let entities: Vec<_> = self.tabs[i]

src/app/commands/mod.rs

@@ -462,6 +462,7 @@ inventory::submit!(crate::command::CommandRegistration {
         "EXPORT",
         "EXPORTSTEP",
         "EXPORTSTL",
+        "EXTRIM",
         "FILETAB",
         "FIND",
         "FLATTEN",