Always save chats to disk, but save them as text by default. This also changes

the UI behavior to always open a 'New Chat' and setting it as current instead
of setting a restored chat as current. This improves usability by not requiring
the user to wait if they want to immediately start chatting.

gpt4all-chat/chat.h

@@ -54,6 +54,8 @@ public:
     }
     ChatModel *chatModel() { return m_chatModel; }
 
+    bool isNewChat() const { return m_name == tr("New Chat") && !m_chatModel->count(); }
+
     Q_INVOKABLE void reset();
     Q_INVOKABLE void processSystemPrompt();
     Q_INVOKABLE bool isModelLoaded() const;