- Add KB agent fallback support in useQuickChat and allow switching sessions by agent plus model override
- Introduce session target key matching so same target reloads messages while different model selections create distinct sessions
- Update QuickChatFAB to lazy-load models, show model override UI, and keep quick chat usable for model-only conversations
- Add and expand hook/component tests to cover model selection flows, KB session creation, and default-model reset behavior
