feat(stretch): live ghost preview while dragging the new point

STRETCH now shows a live ghost where vertices inside the crossing window
follow the cursor and the rest stay anchored, instead of only a rubber-band
line. Add WireModel::stretched and pass the selection's wires into the
command.

Co-Authored-By: Claude Opus 4.8 <[email protected]>

src/app/commands.rs

@@ -1567,7 +1567,8 @@ impl OpenCADStudio {
                     self.tabs[i].active_cmd = Some(Box::new(cmd));
                 } else {
                     use crate::modules::home::modify::stretch::StretchCommand;
-                    let new_cmd = StretchCommand::new(handles);
+                    let wires = self.tabs[i].scene.wire_models_for(&handles);
+                    let new_cmd = StretchCommand::new(handles, wires);
                     self.command_line.push_info(&new_cmd.prompt());
                     self.tabs[i].active_cmd = Some(Box::new(new_cmd));
                 }