Fix bug where editing a citation would cause a spurious \u2060 "Word Joi...

Fix bug where editing a citation would cause a spurious \u2060 "Word Joiner" character to be inserted where the caret is, triggering an "Undo Manual Format" prompt on the subsequent refresh.

Improve "Undo Edit" and "Merge Citation" hint dialogs by using only one "OK" button and adding an exclamation point icon.

MD-20848
MD-20849