Port the Mistral families, including the release date logic

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

@@ -0,0 +1,27 @@
+using static AIStudio.Provider.Capability;
+
+namespace AIStudio.Models.Mistral;
+
+/// <summary>
+/// Mistral Medium, which could see for almost a year before it could think.
+/// </summary>
+public sealed class MistralMediumFamily : 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 Medium 3 on, reasoning from Mistral Medium 3.5 on.");
+
+    /// <inheritdoc />
+    protected override int VisionSince => 2505;
+
+    /// <inheritdoc />
+    protected override int ReasoningSince => 2604;
+
+    /// <inheritdoc />
+    protected override int LatestRelease => 2604;
+
+    /// <inheritdoc />
+    protected override void Declare(ModelFamilyBuilder builder) =>
+        builder.Rule("mistral-medium").AsSegment()
+            .Capabilities(WHAT_THEY_COULD_ALWAYS_DO)
+            .Apis(CHAT_COMPLETION_API);
+}