Quran originally without vowel marks?

I've come across the claim that the first mushafs (suhuf?) did not include vowel marks and sometimes did not even consistently use other diacritical marks to distinguish consonants. An example of a page of a very early mushaf that lacks vowel marks is the [Sana'a manuscript](https://en.wikipedia.org/wiki/Sana 'a_manuscript). This leads to the questions: - When were consistent vowel marks and other diacritical marks added, according to Islamic lore? (Asking for historical evidence would be a better fit on [History](https://history.stackexchange.com/) , but if any is available, it will be interesting here as well.) - If we leave out all vowel marks from the current canonical text, are there passages that become ambiguous? As an example, I've heard the claim that at the beginning of surah [Rum](https://quran.com/30/) , one of the verses could then be read as either "the Romans will defeat" or "the Romans will be defeated". - Does early Islamic scholarship discuss these issues?