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/test/canvas-model-policy.test.ts

@@ -1,7 +1,7 @@
 import { describe, expect, test } from "bun:test";
 
 import { canvasConnectionError } from "../src/lib/canvas/canvas-connection-policy";
-import { buildGenerationConfig, resolveCanvasGenerationModel } from "../src/lib/canvas/canvas-project-generation";
+import { assertCanvasImageReferenceLimit, buildGenerationConfig, canvasImageReferenceLimitError, resolveCanvasGenerationModel } from "../src/lib/canvas/canvas-project-generation";
 import { defaultModelCapabilityConfig } from "../src/lib/model-capabilities";
 import { groupModelsByDisplayName, modelCompatibilityError, modelGroupReferenceLimits, resolveCompatibleModel } from "../src/lib/model-selection";
 import { defaultConfig, type AiConfig, type ModelChannel } from "../src/stores/use-config-store";
@@ -124,3 +124,20 @@ describe("画布连线能力", () => {
         expect(canvasConnectionError(config, nodes, [], { fromNodeId: "character", toNodeId: "target" })).toBe("");
     });
 });
+
+describe("图片参考图上限", () => {
+    test("超出当前模型上限时保留全部输入并返回明确错误", () => {
+        const config = policyConfig();
+        const modelCost = config.channels[0]?.modelCosts?.[0];
+        if (!modelCost?.capabilityConfig?.image) throw new Error("缺少图片能力配置");
+        modelCost.capabilityConfig.image.references.maxImages = 1;
+        const references = [
+            { id: "image-a", name: "image-a.png", type: "image/png", dataUrl: "data:image/png;base64,YQ==" },
+            { id: "image-b", name: "image-b.png", type: "image/png", dataUrl: "data:image/png;base64,Yg==" },
+        ];
+
+        expect(canvasImageReferenceLimitError(config, references)).toContain("最多支持 1 张参考图，当前已连接 2 张");
+        expect(() => assertCanvasImageReferenceLimit(config, references)).toThrow("请移除多余连线后重试");
+        expect(references).toHaveLength(2);
+    });
+});