feat: add guarded image generation controls

src/utils/imageGeneration.ts

@@ -0,0 +1,13 @@
+export type ImageGenerationMode = 'auto' | 'required' | 'disabled';
+
+export const IMAGE_GENERATION_MODE_LABELS: Record<ImageGenerationMode, string> = {
+  auto: '自动识别',
+  required: '强制开启',
+  disabled: '关闭',
+};
+
+export function nextImageGenerationMode(mode: ImageGenerationMode): ImageGenerationMode {
+  if (mode === 'auto') return 'required';
+  if (mode === 'required') return 'disabled';
+  return 'auto';
+}