chore: update last-release-sha for next release

chore(version): Bump version and update changelog for 1.25.1

chore(version): Bump version and update changelog for 1.25.0

Merge #4455

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COPYBARA_INTEGRATE_REVIEW=#4455 from google:release/candidate f660ec8
PiperOrigin-RevId: 868877872

chore(version): Bumps version to 1.24.1 patch

Co-authored-by: Wei Sun (Jack) <weisun@google.com>
PiperOrigin-RevId: 866107525

chore(version): Bump version and update changelog for 1.24.0

Co-authored-by: Wei Sun (Jack) <weisun@google.com>
PiperOrigin-RevId: 865651579

chore: Bumps version to v1.23.0 and updates CHANGELOG.md

Co-authored-by: Kathy Wu <wukathy@google.com>
PiperOrigin-RevId: 859790616

chore: Bumps version to v1.22.1 and updates CHANGELOG.md

Fixing two bugs found in v1.22.0.

Co-authored-by: Liang Wu <wuliang@google.com>
PiperOrigin-RevId: 855343807

fix: map LiteLLM thought parts to reasoning_content

- Treat Part(thought=True) as reasoning_content when building assistant messages.
- Add unit tests for thought-only and thought+text cases.

Close #4069

Co-authored-by: George Weale <gweale@google.com>
PiperOrigin-RevId: 853790274

chore: Bumps version to v1.21.0 and updates CHANGELOG.md

Co-authored-by: Xiang (Sean) Zhou <seanzhougoogle@google.com>
PiperOrigin-RevId: 843427582

chore: Bumps version to v1.20.0 and updates CHANGELOG.md

Co-authored-by: Ankur Sharma <ankusharma@google.com>
PiperOrigin-RevId: 839930279