A terse, altered "Hello" is all I say. Sometimes I don't say anything. Most humans would wait a few seconds then prompt with "...Hello?", whereas bots tend to hang up after ~2s silence

That's my experience too. I mostly don't pick up calls from numbers that I don't recognize. On the very rare occasion that I am expecting such a call, I always stay silent after picking up. A real human will without fail start talking after a second or two.

When it is a human scam caller, what I sometimes do is to say "Hello" and then, when they start talking, and I can already guess they are full of shit, I act as if I am not hearing them properly and say "Hello?? Heeellooo? Hello?" Then they hang up lol.

Don’t you guys have phones that screen calls?