feat: add GPT-4 to GitHub Copilot provider

open-sse/config/providerModels.js

@@ -65,6 +65,7 @@ export const PROVIDER_MODELS = {
     { id: "gemini-2.5-flash", name: "Gemini 2.5 Flash" },
   ],
   gh: [  // GitHub Copilot - OpenAI models
+    { id: "gpt-4", name: "GPT-4" },
     { id: "gpt-4o", name: "GPT-4o" },
     { id: "gpt-4o-mini", name: "GPT-4o mini" },
     { id: "gpt-4.1", name: "GPT-4.1" },