Fixed and improved the system prompt of chats started from assistants (#1172)

app/MindWork AI Studio/Assistants/ChatSystemPromptSource.cs

@@ -0,0 +1,26 @@
+namespace AIStudio.Assistants;
+
+/// <summary>
+/// Where the system prompt of a chat comes from which continues the conversation of an assistant.
+/// </summary>
+/// <remarks>
+/// Assistant plugins name these values in their key ChatSystemPrompt, so the names must not change.
+/// </remarks>
+public enum ChatSystemPromptSource
+{
+    /// <summary>
+    /// The default prompt of AI Studio, which a new chat without a chat template gets as well.
+    /// </summary>
+    AI_STUDIO_DEFAULT,
+
+    /// <summary>
+    /// The prompt with which the assistant ran its conversation.
+    /// </summary>
+    ASSISTANT,
+
+    /// <summary>
+    /// A prompt which the assistant writes for the chat, e.g., because its own prompt forbids follow-up questions
+    /// or demands JSON.
+    /// </summary>
+    CUSTOM,
+}