Read the context window from four more model lists

app/MindWork AI Studio/Provider/OpenRouter/OpenRouterModel.cs

@@ -1,8 +1,16 @@
+using System.Text.Json.Serialization;
+
 namespace AIStudio.Provider.OpenRouter;
 
 /// <summary>
 /// A data model for an OpenRouter model from the API.
 /// </summary>
+/// <remarks>
+/// The window is the model's, not that of any one provider behind it. OpenRouter also states a
+/// window per provider it currently prefers, but it picks one per request, so a number taken from
+/// there would describe a choice nobody has made yet.
+/// </remarks>
 /// <param name="Id">The model's ID.</param>
 /// <param name="Name">The model's human-readable display name.</param>
-public readonly record struct OpenRouterModel(string Id, string? Name);
+/// <param name="ContextWindowTokens">How much the model reads and writes in one conversation, in tokens.</param>
+public readonly record struct OpenRouterModel(string Id, string? Name, [property: JsonPropertyName("context_length")] int? ContextWindowTokens);