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

feat: Propagate `application_name` set for the BigQuery Tools as BigQ…

…uery job labels

This change will help the tools user identify per agent job usage in BQ console and INFORMATION_SCHEMA views. This change fulfills the feature request #3582. Here is a demo after change: screen/C6YB4ge2FM2ZREi.

PiperOrigin-RevId: 834480140

fix: Update dependency version constraints to be based on PyPI versions

Co-authored-by: Yeesian Ng <ysian@google.com>
PiperOrigin-RevId: 828460860

chore:Rename conformance `create` command to `record`

PiperOrigin-RevId: 822708044

feat: Set agent_state in invocation context right before yielding the…

… checkpoint event

PiperOrigin-RevId: 816804179

fix: unbreak client closed errors when using vertexai session service

PiperOrigin-RevId: 811911528

Release v1.15.0