refactor: migrate io-intelligence provider to AI SDK (#11262)

Migrates the IO Intelligence provider from legacy BaseOpenAiCompatibleProvider
(direct openai SDK) to OpenAICompatibleHandler (Vercel AI SDK).

- Extends OpenAICompatibleHandler instead of BaseOpenAiCompatibleProvider
- Uses getModelParams for model parameter resolution
- Updates tests to mock ai module's streamText/generateText

Author: daniel-lxs