I would use ai because that groups all the topics using a feature of the official AI plugin. It’s in the “official plugin” group.
And the plugin topic says that topics should be
I expected ask-ai to be in the “Discourse AI Features” group. It currently isn’t. But the group requires the ai tag to be added first, and I think that makes sense. Every topic that is about a feature of the AI plugin is also about the AI plugin.
I am not sure I would include search. To me, ask-ai and search are the two options in search, so if the topic was about something affecting both or the combination of them, I would add both. Otherwise, I would probably only use ask-ai.