Reworked the Hugging Face provider (#944)

app/MindWork AI Studio/Provider/ProviderRequestFailureReason.cs

@@ -5,4 +5,13 @@ public enum ProviderRequestFailureReason
     NONE,
     INSUFFICIENT_QUOTA,
     TOO_MANY_REQUESTS,
+
+    /// <summary>
+    /// The provider does not serve the requested model.
+    /// </summary>
+    /// <remarks>
+    /// This applies to gateways which route to other providers: the model exists, but the one
+    /// meant to answer for it does not offer it.
+    /// </remarks>
+    MODEL_NOT_SUPPORTED_BY_PROVIDER,
 }