Show selected OpenAI model in Settings picker

[jdisho]

Problem

Currently, there is no visual indication of the active model in the Settings. When users open the model selection view for summarization, interpretation, and multiple source implementation, it always defaults to displaying the first option, regardless of which model is actually selected.

This creates two usability issues:

• First-time users cannot distinguish between the default model and a manually selected one.
• Users cannot verify which model they are currently using.

Solution

Display the selected model's name within the picker to reflect the active selection even when the picker is closed. If no model has been explicitly selected, indicate the default model.

Additional context

No response

Code of Conduct

• I agree to follow this project's Code of Conduct and Contributing Guidelines

[PSchmiedmayer]

Sounds like a great idea; could be a nice secondary label.

[jdisho]

Note: All these section items lead to views that are part of SpeziLLM/SpeziLLMOpenAI. Would be better to wait for StanfordSpezi/SpeziLLM#64 to merge to avoid conflicts or duplication.