fix(mtext): keep arrows in editor

Route captured arrows to the MText caret only while the hidden command input retains focus.\n\nRefs #655

src/app/view/mod.rs

@@ -2266,6 +2266,7 @@ impl OpenCADStudio {
                         {
                             return Some(Message::CommandLineArrowProbe {
                                 direction: arrow?,
+                                extend_selection: modifiers.shift(),
                             });
                         }
                         // A focused web text field needs the browser clipboard;