feat(canvas): 画布媒体工作流 - 支持批量连线、失败重试与模型能力增强

合并 PR #230。保留当前主线样式与组件结构，吸收批量连线、失败批次重试、媒体模型能力和相关后端增强，并修复集成检查发现的分辨率选择器启用条件与测试稳定性问题。

web/test/canvas-emotion-edit-plan.test.ts

@@ -0,0 +1,45 @@
+import { describe, expect, test } from "bun:test";
+
+import { buildEmotionPrompt, emotionProviderMask, normalizeEmotionPromptForProvider, resolveEmotionEditPlan } from "../src/lib/canvas/canvas-emotion";
+
+const faceBox = { id: "face-1", x: 120, y: 80, width: 160, height: 180, source: "detected" as const };
+const editRegion = { x: 40, y: 20, width: 320, height: 360 };
+
+describe("emotion edit provider plan", () => {
+    test("keeps provider mask when the selected image model supports it", () => {
+        expect(resolveEmotionEditPlan(true)).toEqual({ mode: "provider-mask", includeMask: true });
+    });
+
+    test("falls back visibly to local compositing when the provider does not support masks", () => {
+        const plan = resolveEmotionEditPlan(false);
+        expect(plan).toEqual({
+            mode: "local-composite",
+            includeMask: false,
+            notice: "当前渠道不支持蒙版，使用脸部裁切与本地羽化融合",
+        });
+        expect(emotionProviderMask(plan, { dataUrl: "data:image/png;base64,bWFzaw==" })).toBeUndefined();
+    });
+
+    test("does not promise a provider mask in the shared emotion prompt", () => {
+        const prompt = buildEmotionPrompt(
+            { presetId: "emotion-0-0", intimacy: 0, arousal: 0, characterName: "角色1", faceBox },
+            editRegion,
+        );
+
+        expect(prompt).not.toContain("透明蒙版");
+        expect(prompt).not.toContain("白色蒙版");
+        expect(prompt).toContain("目标人脸框");
+    });
+
+    test("removes legacy mask promises before retrying an existing emotion node", () => {
+        const legacyPrompt = [
+            "只允许修改目标框及其透明蒙版对应的这一张脸。",
+            "输入图已裁切到目标人物头部区域；透明蒙版内允许编辑，白色蒙版区域必须保持不变，蒙版外绝对不要生成或修改任何内容。",
+        ].join("\n");
+
+        const prompt = normalizeEmotionPromptForProvider(legacyPrompt);
+        expect(prompt).not.toContain("透明蒙版");
+        expect(prompt).not.toContain("白色蒙版");
+        expect(prompt).toContain("目标人脸框及其邻近表情区域");
+    });
+});