Move the model kinds into the rule engine

app/MindWork AI Studio/Models/Mistral/VoxtralFamily.cs

@@ -1,3 +1,5 @@
+using AIStudio.Provider;
+
 using static AIStudio.Provider.Capability;
 
 namespace AIStudio.Models.Mistral;
@@ -9,6 +11,11 @@ namespace AIStudio.Models.Mistral;
 /// They take speech as input and answer in text, which makes them neither a chat model nor a
 /// transcription model but something in between: they understand what was said rather than only
 /// writing it down.
+///
+/// The app has to pick one of the two all the same, and the provider decides it: asking Mistral for
+/// a chat completion with voxtral-mini-latest is answered with "Invalid model". So they are
+/// transcription models, which is what keeps them out of the chat list, while the capabilities above
+/// still say what they understand.
 /// </remarks>
 public sealed class VoxtralFamily : ModelFamily
 {
@@ -16,11 +23,12 @@ public sealed class VoxtralFamily : ModelFamily
     public override ModelVendor Vendor => ModelVendor.MISTRAL_AI;
 
     /// <inheritdoc />
-    public override ModelSource Source => new("https://docs.mistral.ai/getting-started/models/models_overview/", new DateOnly(2026, 9, 11), "Ported unchanged from the rules in ProviderExtensions.OpenSource.cs: speech in, text out, tool calling.");
+    public override ModelSource Source => new("https://docs.mistral.ai/getting-started/models/models_overview/", new DateOnly(2026, 9, 12), "Capabilities ported unchanged from ProviderExtensions.OpenSource.cs: speech in, text out, tool calling. That they count as transcription models comes from Provider/ModelKindExtensions.cs.");
 
     /// <inheritdoc />
     protected override void Declare(ModelFamilyBuilder builder) =>
         builder.Rule("voxtral").AsSegment()
             .Capabilities(TEXT_INPUT | SPEECH_INPUT | TEXT_OUTPUT | FUNCTION_CALLING)
-            .Apis(CHAT_COMPLETION_API);
+            .Apis(CHAT_COMPLETION_API)
+            .Kind(ModelKind.TRANSCRIPTION);
 }