fix(canvas): 画布图片生成 - 参考图超限时停止生成并提示清理连线

保留全部已连接参考图，在首次生成、重试和任务入口统一校验模型上限。

web/src/lib/canvas/canvas-project-generation.ts

@@ -52,14 +52,14 @@ export async function runBackendCanvasGenerationTask(
     },
     dependencies?: GenerationTaskDependencies,
 ) {
-    const normalizedReferenceImages = mode === "image" ? limitCanvasImageReferences(config, referenceImages) : referenceImages;
+    if (mode === "image") assertCanvasImageReferenceLimit(config, referenceImages);
     return runBackendGenerationTask(
         {
             projectId,
             mode,
             prompt,
             config,
-            referenceImages: normalizedReferenceImages,
+            referenceImages,
             referenceVideos,
             referenceAudios,
             mask,
@@ -74,12 +74,15 @@ export async function runBackendCanvasGenerationTask(
     );
 }
 
-// Canvas references can include a scene frame plus multiple character turnarounds. Keep
-// the earliest connected scene image when a provider accepts fewer images than the graph.
-export function limitCanvasImageReferences(config: AiConfig, referenceImages: ReferenceImage[]) {
+export function canvasImageReferenceLimitError(config: AiConfig, referenceImages: ReferenceImage[]) {
     const maxImages = modelCapabilityConfigFor(config, config.model).image?.references.maxImages;
-    if (maxImages === undefined || maxImages < 1 || referenceImages.length <= maxImages) return referenceImages;
-    return referenceImages.slice(0, maxImages);
+    if (maxImages === undefined || referenceImages.length <= maxImages) return "";
+    return `当前图片模型最多支持 ${maxImages} 张参考图，当前已连接 ${referenceImages.length} 张。请移除多余连线后重试`;
+}
+
+export function assertCanvasImageReferenceLimit(config: AiConfig, referenceImages: ReferenceImage[]) {
+    const error = canvasImageReferenceLimitError(config, referenceImages);
+    if (error) throw new Error(error);
 }
 
 export { backendProviderConfig };