Clear undos when starting a new interaction in the listener

basis/ui/tools/listener/history/history.factor

@@ -22,9 +22,8 @@ TUPLE: history document elements index ;
     unless-empty ;
 
 : update-document ( history -- )
-    [ [ index>> ] [ elements>> ] bi nth string>> ]
-    [ document>> ] bi
-    set-doc-string ;
+    [ [ index>> ] [ elements>> ] bi nth string>> ] [ document>> ] bi
+    [ set-doc-string ] [ clear-undo drop ] 2bi ;
 
 : change-history-index ( history i -- )
     over elements>> length 1-

basis/ui/tools/listener/listener.factor

@@ -85,7 +85,9 @@ M: object (print-input)
 
 : interactor-finish ( interactor -- )
     [ history>> history-add ] keep
-    [ print-input ] [ clear-editor drop ] 2bi ;
+    [ print-input ]
+    [ clear-editor drop ]
+    [ model>> clear-undo drop ] 2tri ;
 
 : interactor-eof ( interactor -- )
     dup interactor-busy? [