Links emitted in Google AI Mode are marked with a rel="noreferrer" attribute, which causes browsers to not send the Referer header (or to strip it) when navigating. That means a click from AI Mode may show up with no referrer (i.e. “direct / unknown”) rather than as a Google domain.
Google AI Mode links contain /#:~:text= (text fragment in deep-links), which you could use to create conditions for Marketing Channel processing rules or Segments.
So,
Marketing Channel Processing Rule:
If Page URL (or Query String) contains "#:~:text="
Then Set Channel = "AI Search (Google AI Mode)"
Segment in Adobe Analytics/CJA:
Page URL contains "#:~:text="
CJA Derived Field:
IF(contains(Page URL, "#:~:text="), "Yes", "No")
Because AI Mode changes how users find and click content, I'd recommend treating it as a separate channel.