Here are the things I tried to tackle on this PR:

- Make the compaction call stand out a bit more from other regular tool
calls
- Make text size of the compaction's markdown output be consistent with
the thread body text
- Don't show regular thread loading spinner while compaction is in
progress, given that has its own spinner
- Add a different icon than scissors for compaction and add it to the
autocomplete menu so its consistent w/ skills items

<img width="600" alt="Screenshot 2026-06-09 at 10  57@2x"
src="https://github.com/user-attachments/assets/5c3d25af-aa49-42e1-b6b6-c3f95c664456"
/>

Release Notes:

- N/A