Yeah-no Definition

interjection

(emphatic, colloquial) Used sarcastically to answer "no" to a question where the negative answer should have been obvious.

Wiktionary
Non-commital expression with various applications, including: denotation of conclusion of cursory difference(s) of opinion between speakers ("yeah-nah, he's a top bloke at the end of the day"), and/or perceived escalations of discord ("yeah-nah, I can, however, see where you're coming from")
Wiktionary