- Introduced `CleanJSONSchemaForAntigravityResponse` to process schemas without adding tool-specific placeholders. - Updated `cleanJSONSchema` with `removeGeminiMetadata` parameter for improved schema control. - Refactored Antigravity schema sanitization to handle declaration and generation paths independently. - Mapped OpenAI `response_format` to Antigravity settings, ensuring proper response schema cleaning. - Expanded tests to verify proper placeholder-free response schema handling and metadata preservation. Closes: #4652