Allow control of the length of an AI summary

[Falco]

@markschmucker

but are the single-sentence summaries used anywhere?

They are the topic list summaries like

@markschmucker

And are they available via the API?

They are serialized in the existing topic list routes when enabled and the requesting user can access to it.

We are finishing the feature set for release this week, and will have an announcement and documentation of it in the next days.

@markschmucker

Is controlling the length still on the roadmap?

Customizing prompts is something we still want to do, and I hope to achieve it by Q2 2025.