The site you cite for [3] reads:
"Khamenei, the leader of the great nation of Iran, the freedom seekers of the world and the Islamic nations, has joined the highest paradise and reached his long-cherished wish of martyrdom in the holy month of Ramadan," said an announcement aired on Iranian state television.
Sounds to me like it was made up after the fact.
In Islam, a Muslim who dies in war is considered a martyr, and it's desirable to die in the month of Ramadan. In other words, it's something that most Muslims want to have happen, but it's not like something we want to make happen. Like I don't want to die right now, but if I were to die, may as well be during Ramadan.
Extracting an 80 year old from their house is a bit harder than you might expect. Even if their stubborness is going to get them killed.
I personally have difficulty believing Iran didn't know that war was inbound, everyone I talk to was anticipating it within a roughly 3-week window and these are people just working off what they read on internet news. Khamenei might not have known he was going to die that day and if he had his family would probably have been elsewhere. But it seems pretty reasonable to assume that he was purposefully not raising his security in his final days. The narrative win of a calm death vs the perfidious Israeli attack is powerful enough that he must have considered it.
There is an understanding that the strike that took him out also took out a lot of visiting high-level leaders; that'd be quite strong evidence against the idea it was intentional. But the fog of war is thick and it doesn't seem safe to take that occurrence as a given yet.