refactor(ai): Update LLM implementations to use Model objects

- LLM constructors now take Model objects instead of string IDs
- Added provider field to AssistantMessage interface
- Updated getModel function with type-safe model ID autocomplete
- Fixed Anthropic model ID mapping for proper API aliases
- Added baseUrl to Model interface for provider-specific endpoints
- Updated all tests to use getModel for model instantiation
- Removed deprecated models.json in favor of generated models

packages/ai/src/index.ts

@@ -24,7 +24,7 @@ export {
 
 // Export providers
 export { AnthropicLLM } from "./providers/anthropic.js";
-export { GoogleLLM } from "./providers/gemini.js";
+export { GoogleLLM } from "./providers/google.js";
 export { OpenAICompletionsLLM } from "./providers/openai-completions.js";
 export { OpenAIResponsesLLM } from "./providers/openai-responses.js";