MB7's CF-52 sweep retired three drift-prone NATIVE_SELECT_CLASS clones
behind the shared NativeSelect primitive. The AI provider section
carried five more raw <select> declarations with their own copy of the
border + bg + height contract — exactly the drift the primitive was
introduced to cure. Swap them over so the AI provider, OpenAI model,
Anthropic model, local model, and Add-provider pickers all render
through the same styled wrapper as the rest of Settings.