Let tool results restrict a chat to self-hosted providers

app/MindWork AI Studio/Chat/ChatThread.cs

@@ -106,6 +106,26 @@ public sealed record ChatThread
             this.RequiredProviderConfidence = minimumProviderConfidence;
     }
 
+    /// <summary>
+    /// Tightens the data security of this chat to what the data brought in demands, and never
+    /// loosens it.
+    /// </summary>
+    /// <remarks>
+    /// Data which may only be used with self-hosted providers keeps the chat restricted to them,
+    /// no matter what comes in later: the data was seen by this chat. Data which may be used with
+    /// any provider marks the chat as one which holds data of a data source, while a restriction set
+    /// earlier stays. NOT_SPECIFIED demands nothing and changes nothing.<br/><br/>
+    /// Shared by the RAG process and by tools which search the data sources, so both tighten a chat
+    /// the same way.
+    /// </remarks>
+    /// <param name="dataSecurity">What the data brought in demands.</param>
+    public void RequireDataSecurity(DataSourceSecurity dataSecurity) => this.DataSecurity = (this.DataSecurity, dataSecurity) switch
+    {
+        (DataSourceSecurity.SELF_HOSTED, _) or (_, DataSourceSecurity.SELF_HOSTED) => DataSourceSecurity.SELF_HOSTED,
+        (_, DataSourceSecurity.ALLOW_ANY) => DataSourceSecurity.ALLOW_ANY,
+        _ => this.DataSecurity,
+    };
+
     /// <summary>
     /// The name of the chat thread. Usually generated by an AI model or manually edited by the user.
     /// </summary>