Welcome to Librarium Online!
I was having a discussion with my friend and im new to tabletop, and i was wondering whether you could field a jetbike seer council unit in a battle as another craftworld, such as alaitoc, or a custom one
If you build it based on the main codex, then yea.
so if i built a jetbike seer council, where would i be able to find the stats because i cant find it in my codex
A seer council is just a farseer with warlock squad
Well, just to be clear we are sort of abusing language here a little and that might be what has the OP confused.
A "seer council" actually used to be a unit with a bunch of special rules from the old craftworld codex. However people with them actually won some tournaments, so GW gave seer councils the axe. No army can field a true seer council anymore. Period. No seer councils.
However if you take a unit of warlocks from the current codex and you have a farseer join them as an independent character, than we call that a "seer council" on this forum even though, really, it is only a pale shadow of what once was. But it's shorter to type "seer council" than "squad of warlocks with a farseer attached" and since there are no true seer councils anymore it isn't confusing for us; so the term is useful.
I don't know if the words "seer council" appear anywhere in the current codex actually.