- Use parametersJsonSchema instead of parameters for Gemini tool declarations
to support full JSON Schema (anyOf, oneOf, const, etc.)
- Keep legacy parameters field for Claude models on Cloud Code Assist, where
the API translates parameters into Anthropic's input_schema
- Revert claude-opus-4-6-thinking back to claude-opus-4-5-thinking (model
doesn't exist on the Antigravity endpoint)
fixes#1398