feat(models): update Google model configurations

[gmh5225]

Relates to

Models configuration update for Google Gemini

• Add gemini-2.0-flash-exp for SMALL/MEDIUM/LARGE class
• Update default models to latest versions

Risks

Low - Model configuration update only, no functional changes to core system

Background

What does this PR do?

Updates the Google Gemini model configurations to include latest versions and experimental models:

• Add gemini-2.0-flash-exp for SMALL/MEDIUM/LARGE class
• Update default models to latest versions

What kind of change is this?

Updates (new versions of included code)

Documentation changes needed?

My changes do not require a change to the project documentation.

Testing

Where should a reviewer start?

Check the model configurations in packages/core/src/models.ts

Detailed testing steps

1. Verify model configurations are correctly set for each class:
   • SMALL: gemini-2.0-flash-exp
   • MEDIUM: gemini-2.0-flash-exp
   • LARGE: gemini-2.0-flash-exp
2. Test model selection logic works with new configurations
3. Verify fallback to default models works as expected

Deploy Notes

Standard deployment, no special steps required

[monilpat]

LGTM thanks much needed