Add one model host per provider and the unwrapping walk

app/MindWork AI Studio/Models/Hosting/Hosts/HostX.cs

@@ -0,0 +1,15 @@
+using AIStudio.Provider;
+
+namespace AIStudio.Models.Hosting.Hosts;
+
+/// <summary>
+/// xAI's own API, where Grok comes from.
+/// </summary>
+public sealed class HostX : ModelHost
+{
+    /// <inheritdoc />
+    public override LLMProviders Provider => LLMProviders.X;
+
+    /// <inheritdoc />
+    public override ModelSource Source => new("https://docs.x.ai/docs/api-reference", new DateOnly(2026, 9, 11), "Models are named plainly, and the app reaches them through the OpenAI-compatible endpoint.");
+}