Implement fuzzyMatchModel() for case-insensitive substring matching with provider filtering. Add fetchAvailableModels() to get available models from OpenCode client with caching.
Ultraworked with [Sisyphus](https://github.com/code-yeongyu/oh-my-opencode)
Co-authored-by: Sisyphus <clio-agent@sisyphuslabs.ai>
justsisyphus