- Create ModelSelectionModal component with list-style interface
- Add brain emoji (🧠) indicator below chat input, left-aligned
- Show current model name in lowercase or red X if not configured
- Fullscreen modal displays all available models with configuration status
- Green checkmark for configured models, red alert for unconfigured
- Integrate with existing API key management and model selection logic
- Modal handles API key setup workflow when selecting unconfigured models
- Clean separation between compact indicator and full selection interface
