Port the OpenAI families and add the model registry

app/MindWork AI Studio/Models/OpenAI/Gpt35Family.cs

@@ -0,0 +1,33 @@
+using static AIStudio.Provider.Capability;
+
+namespace AIStudio.Models.OpenAI;
+
+/// <summary>
+/// GPT-3.5, which answers with text and does nothing else.
+/// </summary>
+public sealed class Gpt35Family : ModelFamily
+{
+    /// <inheritdoc />
+    public override ModelVendor Vendor => ModelVendor.OPEN_AI;
+
+    /// <inheritdoc />
+    public override ModelSource Source => new("https://platform.openai.com/docs/models", new DateOnly(2026, 9, 11), "Ported unchanged from the rules in ProviderExtensions.OpenAI.cs: text in, text out, no tools and no images.");
+
+    /// <inheritdoc />
+    protected override void Declare(ModelFamilyBuilder builder)
+    {
+        builder.Rule("gpt-3.5").AsPrefix()
+            .Capabilities(TEXT_INPUT | TEXT_OUTPUT)
+            .Apis(CHAT_COMPLETION_API);
+
+        //
+        // The odd one out, and kept odd on purpose: the previous rules put this one model on the
+        // Responses API and every other GPT-3.5 on the chat completion API. It reads like an
+        // oversight, but what the app answers today is what the snapshot pins, and correcting it is
+        // a decision of its own rather than something to slip into a port.
+        //
+        builder.Rule("gpt-3.5-turbo").AsExact()
+            .Capabilities(TEXT_INPUT | TEXT_OUTPUT)
+            .Apis(RESPONSES_API);
+    }
+}