agent: Fix new thread model selection when starting new thread (#34708)

Release Notes:

- agent: Fixed an issue where clicking on "Start New Thread" in the
agent configuration would not always switch to the correct
provider/model
4002801034Bennet Bo Fenner committed on 7/18/2025, 1:58:44 PM· committed by GitHubparentfd8480a
1 file changedLine totals unavailable