bedrock: Preserve thinking blocks for Bedrock (#29602)

Fixes a regression from #29055, resolves #29290

Release Notes:

- agent: Fixed a regression that rendered Claude 3.7 Thinking unusable
on Bedrock.
fa40353fc5Shardul Vaidya committed on 4/29/2025, 4:18:32 PM· committed by GitHubparent83b8530
2 files changedLine totals unavailable