Fix Ollama Kotlin function callback integration tests

[sobychacko]

• Add default values to KotlinRequest data class to fix Jackson deserialization
• Replace hardcoded model name with OllamaModel.LLAMA3_2 for consistency
• Extract common test setup into companion objects for Ollama tests
• Replace var with val using when expression in weather service
• Clean up imports and remove unused annotations
• Standardize property access using Kotlin conventions

[markpollack]

merged in 5e1f681da25ee4895b3ef5749698abbdc1da8538