when using 'G' command to move to end fo file, use the 'textLength' field to calculate the new bufferIdx, which is more sensible than using the LineGap's idx for the same purpose

fcore/normal-mode/normal-move.sml

@@ -63,10 +63,9 @@ struct
         } = app
 
       val buffer = LineGap.goToEnd buffer
-      val {line = bufferLine, idx = bufferIdx, ...} = buffer
+      val {line = bufferLine, textLength, ...} = buffer
 
-      val bufferIdx = bufferIdx - 1
-      val bufferIdx = Cursor.clipIdx (buffer, bufferIdx)
+      val bufferIdx = Int.max (0, textLength - 2)
       val bufferLine = bufferLine - 1
 
       val buffer = LineGap.goToIdx (bufferIdx, buffer)