Port the Mistral families, including the release date logic

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

@@ -0,0 +1,27 @@
+using static AIStudio.Provider.Capability;
+
+namespace AIStudio.Models.Mistral;
+
+/// <summary>
+/// Mistral Small, which gained images with 3.1 and reasoning with 4.
+/// </summary>
+public sealed class MistralSmallFamily : MistralReleaseDatedFamily
+{
+    /// <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.Mistral.cs: images from Mistral Small 3.1 on, reasoning from Mistral Small 4 on.");
+
+    /// <inheritdoc />
+    protected override int VisionSince => 2503;
+
+    /// <inheritdoc />
+    protected override int ReasoningSince => 2603;
+
+    /// <inheritdoc />
+    protected override int LatestRelease => 2603;
+
+    /// <inheritdoc />
+    protected override void Declare(ModelFamilyBuilder builder) =>
+        builder.Rule("mistral-small").AsSegment()
+            .Capabilities(WHAT_THEY_COULD_ALWAYS_DO)
+            .Apis(CHAT_COMPLETION_API);
+}