Add Claude Desktop official preset

- Add Claude Desktop Official to the Claude Desktop preset list.
- Treat selected official presets as official mode in the form.
- Cover the official preset with a preset-order regression test.

src/config/claudeDesktopProviderPresets.ts

@@ -134,6 +134,21 @@ const brandedRoutes = (
 };
 
 export const claudeDesktopProviderPresets: ClaudeDesktopProviderPreset[] = [
+  {
+    name: "Claude Desktop Official",
+    websiteUrl: "https://claude.ai/download",
+    category: "official",
+    baseUrl: "",
+    mode: "direct",
+    apiFormat: "anthropic",
+    theme: {
+      icon: "claude",
+      backgroundColor: "#D97757",
+      textColor: "#FFFFFF",
+    },
+    icon: "anthropic",
+    iconColor: "#D4915D",
+  },
   {
     name: "Shengsuanyun",
     nameKey: "providerForm.presets.shengsuanyun",