Improve Agent Mode timeline readability

[marksftw]

Summary

Agent Mode shows reasoning and tool activity in a detailed timeline. Improve that timeline in small, independent steps so users can quickly understand what the Agent is doing and scan longer runs without losing access to details.

Tracked work

• Give completed Agent thoughts descriptive labels #646 — Give completed Agent thoughts descriptive labels
• Persist descriptive Agent thought labels with task history #647 — Persist descriptive Agent thought labels with task history
• Make Agent tool calls compact and easy to recognize #648 — Make Agent tool calls compact and easy to recognize
• Group Agent reasoning and tool calls into collapsible steps #649 — Group Agent reasoning and tool calls into collapsible steps

Approach

Keep each change focused and preserve existing behavior outside its scope. Start with descriptive labels, then add durable persistence, improve individual tool rows, and finally explore grouping related activity into collapsible steps.

Detailed requirements and acceptance criteria belong in the child issues above.

[AnthonyRonning]

I don't think the proposed scenario makes sense because reasoning is separate from tool calling. I don't like the idea of hiding the tool calling inside of thinking as it is streaming in.

I think more thought should go into the streaming look vs finsihed streaming look, tool calling vs content vs reasoning. Because the rebric of scenarios here leaves a lot of edge cases.

[marksftw]

I'm fine leaving the tool calling in the main flow for now. I think long term we'll want hidden behind something by default. It ends up being lots of "shell" and "read" on the screen that the user doesn't always need to see.

Here's an example of lots of tool calls where it would be nice to know what's going on:

Often times the "Thought" area has a good explanation why the reasoning decided to launch the tools. I'd like to use that and surface a short version in the main UI flow so the user has more insight into what's going on.

For example, this "Thought" message is almost already good enough. Have gpt-oss make a shorter version and replace the "Thought" text.

[AnthonyRonning]

Feel free to try a couple things. I think there's a lot of iterative improvements that it would be easier to do instead of one big sweep but if you find an approach that looks and feels good then I'd be curious to see.

[marksftw]

okay, I'll try some steps along the way and see how it goes.