fix(media): update native provider API defaults and UI schema

- OpenAI image default: dall-e-3 → gpt-image-1.5 (dall-e-3 deprecated May 12)
- DashScope: add missing 4:3 and 3:4 aspect ratio mappings
- UI: remove stale MiniMax size/prompt_optimizer params (backend uses aspect_ratio since #630)

internal/tools/create_image.go

@@ -30,7 +30,7 @@ var imageGenProviderPriority = []string{"openrouter", "gemini", "openai", "minim
 // imageGenModelDefaults maps provider names to default image generation models.
 var imageGenModelDefaults = map[string]string{
 	"openrouter": "google/gemini-2.5-flash-image",
-	"openai":     "dall-e-3",
+	"openai":     "gpt-image-1.5",
 	"gemini":     "gemini-2.5-flash-image",
 	"minimax":    "image-01",
 	"dashscope":  "wan2.6-image",

internal/tools/create_image_dashscope.go

@@ -71,6 +71,10 @@ func aspectRatioToDashScopeSize(params map[string]any) string {
 		return "1280*720"
 	case "9:16":
 		return "720*1280"
+	case "4:3":
+		return "1024*768"
+	case "3:4":
+		return "768*1024"
 	default:
 		return "1024*1024"
 	}

ui/web/src/pages/builtin-tools/media-provider-params-schema.ts

@@ -12,22 +12,7 @@ export type ParamField = {
 
 export const MEDIA_PARAMS_SCHEMA: Record<string, Record<string, ParamField[]>> = {
   create_image: {
-    minimax_native: [
-      {
-        key: "size",
-        label: "Size",
-        type: "select",
-        default: "1024*1024",
-        options: [
-          { value: "1024*1024", label: "1:1" },
-          { value: "1280*720", label: "16:9" },
-          { value: "720*1280", label: "9:16" },
-          { value: "1024*768", label: "4:3" },
-          { value: "768*1024", label: "3:4" },
-        ],
-      },
-      { key: "prompt_optimizer", label: "Prompt Optimizer", type: "toggle", default: true },
-    ],
+    minimax_native: [],
     bailian: [
       {
         key: "size",