fix: remove non-functional Antigravity image models from imageRegistry

The models gemini-2.5-flash-preview-image-generation and
gemini-3.1-flash-image-preview were surfacing in the model catalog
via getAllImageModels() from imageRegistry.ts, not from the live
upstream API. Removed them from the image provider registry.

open-sse/config/imageRegistry.ts

@@ -63,10 +63,7 @@ export const IMAGE_PROVIDERS = {
     authType: "oauth",
     authHeader: "bearer",
     format: "gemini-image", // Special format: uses Gemini generateContent API
-    models: [
-      { id: "gemini-2.5-flash-preview-image-generation", name: "Gemini 2.5 Flash Image" },
-      { id: "gemini-3.1-flash-image-preview", name: "Gemini 3.1 Flash Image Preview" },
-    ],
+    models: [],
     supportedSizes: ["1024x1024"],
   },
 

src/app/api/providers/[id]/models/route.ts

@@ -154,15 +154,7 @@ const PROVIDER_MODELS_CONFIG: Record<string, ProviderModelsConfigEntry> = {
     authHeader: "Authorization",
     authPrefix: "Bearer ",
     body: {},
-    parseResponse: (data) => {
-      const excluded = new Set([
-        "gemini-2.5-flash-preview-image-generation",
-        "gemini-3.1-flash-image-preview",
-        "gemini-3-pro-low",
-        "gemini-3-pro-high",
-      ]);
-      return (data.models || []).filter((m: any) => !excluded.has(m.model || m.id));
-    },
+    parseResponse: (data) => data.models || [],
   },
   openai: {
     url: "https://api.openai.com/v1/models",