feat(ui): compatible right-click context menu driven by command options

The viewport context menu is now built from a pure model
(ui::popup::context_menu) rendered by the overlay: while a command runs it
offers Enter / Cancel / every keyword of the command's options() with the
keyword shown as a hint, a Recent Input submenu and M2P; when idle it offers
Repeat, Recent Input, Clipboard, Undo/Redo with history labels, the edit
block (Erase/Move/Copy/Scale/Rotate/Mirror/Draw Order), Isolate, Pan/Zoom,
selection tools, Properties and Options. The default row is anchored under
the pointer and the menu is keyboard-navigable (arrows, Enter, mnemonic
letters; any other key closes it and types into the command line).

Right-click behaviour is a user preference (Options → User Preferences,
SHORTCUTMENU / SHORTCUTMENUDURATION): shortcut menu (commercial solutions default),
time-sensitive, or the previous Enter-first cycle.

LINE gains options() (Close/Undo/eXit).

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

src/modules/draw/draw/line.rs

@@ -71,6 +71,21 @@ impl CadCommand for LineCommand {
         }
     }
 
+    fn options(&self) -> Vec<crate::command::CmdOption> {
+        use crate::command::CmdOption;
+        // Mirrors AutoCAD's LINE prompt: Undo once a point is placed, Close
+        // once a closing segment is possible, eXit always.
+        match self.points.len() {
+            0 => Vec::new(),
+            1 => vec![CmdOption::new("Undo", "U"), CmdOption::new("eXit", "X")],
+            _ => vec![
+                CmdOption::new("Close", "C"),
+                CmdOption::new("Undo", "U"),
+                CmdOption::new("eXit", "X"),
+            ],
+        }
+    }
+
     fn on_point(&mut self, pt: DVec3) -> CmdResult {
         if let Some(&last) = self.points.last() {
             let line = Self::line_between(last, pt);
@@ -185,6 +200,9 @@ impl CadCommand for LineCommand {
                     Some(CmdResult::NeedPoint)
                 }
             }
+            // eXit: end the command keeping every segment drawn so far
+            // (AutoCAD LINE's third keyword).
+            "X" | "EXIT" => Some(CmdResult::Cancel),
             "U" | "UNDO" => {
                 if self.points.len() >= 2 {
                     // Drop the last vertex and revert its committed segment.