You said: “paṭisaraṇa means to provide refuge/protection.”
However, in this meaning of word, I don’t understand why Buddha tell the Brahmin Uṇṇābha like this.
Accayāsi, brāhmaṇa, pañhaṁ, nāsakkhi pañhassa pariyantaṁ gahetuṁ.
This question goes too far, brahmin! You weren’t able to grasp the limit of questioning.
I guess the sutta’s contents presents in this order.
(1) panca indriya
(2) they depend on mano, mano encompass all of them.
(3) mano depends on sati
(4) sati depends on vimutti
(5) vimutti depends on nibbana
(6) nibbana depends on?
(7) That question is outside of the scope of answerability
So I think from (3) to (5) is presenting the outline of way to nibbana.
In this context, the main point is that mano is the most important thing because it plays a central role in the way to nibbana.
But in (6), the point is changing. Because the question is basically like that. “What is the final destination’s destination?” I think that is why Buddha said: “This question goes too far, brahmin! You weren’t able to grasp the limit of questioning.”
So in this context, paṭisaraṇa might mean “depend” or something like that. I think the saraṇa of paṭisaraṇa can be seen the Buddha “saranam” gacchami.
If I was wrong, please tell the correct meaning of it to me.