assistant_context: Fix `thread_summary_model` not getting used in Text Threads (#38859)

Closes https://github.com/zed-industries/zed/issues/37472

Release Notes:

- Fixed an issue in Text Threads where it was using `default_model` even
in case `thread_summary_model` was set.

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Signed-off-by: Umesh Yadav <git@umesh.dev>
c627543b46Umesh Yadav committed on 9/25/2025, 12:41:49 PM· committed by GitHubparentf303a46
2 files changedLine totals unavailable