[FEATURE]: Add Custom Model Names using UI

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Describe the enhancement you want to request

I had difficulty selecting my own OLLAMA models from the OpenCode windows application

I expected to be able to add / remove the OLLAMA models from file > settings > model. Instead I see hard coded models I can select from. This is not an extendable solution, I don't want to use a small itty bitty 9b model.

Please add a way to add custom ollama models without h4cking some magic config file.

Workaround: Edit C:\Users\{yourname}\.config\opencode\opencode.json