Add search to the model picker #160

When a provider exposes a large model catalog, such as OpenRouter through Hermes, the model picker becomes a very long scrolling menu.

Finding a specific model requires manually scanning the entire list. This is especially difficult when many models have similar names or separate batch variants.

A search field in the model picker would make it possible to type part of a provider or model name and quickly narrow the list.

Observed with moi 0.12.0.