fix(ui): edit sketch text from letter interiors (#694)

Edit Text now works from a letter's interior as well as its outline, from the tool and the context menu, and highlights the whole text while editing.

crates/ui-egui/src/lib.rs

@@ -726,6 +726,7 @@ impl SolveApp {
         if let Some(d) = &self.dialog {
             v.extend(d.items());
         }
+        v.extend(sketch_text::highlighted(self));
         v
     }