Spinner moves down while thinking text loads

[roblourens]

Testing #290638

The logic for markdown and the classic "working" spinner was that we didn't want to show the spinner while the response text was loading because it was redundant. I didn't know whether you want to follow the same logic inside the thinking container, if this is by design it's fine.

Screen.Recording.2026-01-27.at.11.24.59.AM.mov

[justschen]

cc. @jo-oikawa @hawkticehurst if you have thoughts on this? it was kind of on purpose so that we'd always be showing some kind of progress in the thinking container, but now that i think about it, when text is streaming we never did show the spinner, so i'm down to lean either way