feat(ai-writing): 素材收集技能调用失败时容错回退到其他技能

默认/选中技能调用失败（超时、报错、全部检索词失败）时不再直接报错，
改用其他技能继续检索：节点 emit skill_error 步骤（带真实原因），配置技能
全部失败且无新素材时跑 fallback 兜底（内置知识库检索优先，再到目录其它已
启用技能）。前端 SkillStepsCard 渲染 skill_error（玫红）/ fallback（琥珀），
时间线展示"技能报错→改用其他技能搜集"。

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

frontend-web/src/open-canvas/components/ai-writing/SkillStepsCard.tsx

@@ -1,5 +1,5 @@
 import { useState } from 'react';
-import { ChevronRight, Sparkles, ListChecks, Zap, Loader2, CheckCircle2, CircleStop, Search } from 'lucide-react';
+import { ChevronRight, Sparkles, ListChecks, Zap, Loader2, CheckCircle2, CircleStop, Search, AlertTriangle, Shuffle } from 'lucide-react';
 import { cn } from '@/lib/utils';
 import type { SkillSearchStep } from '../../types/ai-writing';
 import { CollapseTransition } from './CollapseTransition';
@@ -16,6 +16,8 @@ const STEP_ICON: Record<SkillSearchStep['type'], typeof Sparkles> = {
   select_skills: Sparkles,
   invoke_skill: Zap,
   skill_result: CheckCircle2,
+  skill_error: AlertTriangle,
+  fallback: Shuffle,
   stop_early: CircleStop,
 };
 
@@ -25,6 +27,8 @@ const STEP_LABEL: Record<SkillSearchStep['type'], string> = {
   select_skills: '筛选相关技能',
   invoke_skill: '调用技能',
   skill_result: '检索结果',
+  skill_error: '技能调用失败',
+  fallback: '改用其他技能',
   stop_early: '提前停止',
 };
 
@@ -71,6 +75,9 @@ export function SkillStepsCard({ steps, inProgress }: SkillStepsCardProps) {
             const label = STEP_LABEL[step.type] ?? step.type;
             const isStopEarly = step.type === 'stop_early';
             const isResult = step.type === 'skill_result';
+            // 容错：技能调用失败标红，回退其它技能标琥珀，提示用户"出错了但已自动改用其他技能"
+            const isError = step.type === 'skill_error';
+            const isFallback = step.type === 'fallback';
             const isActive = idx === activeIdx;
             return (
               <li key={idx} className="flex items-start gap-2 text-[11px]">
@@ -79,11 +86,13 @@ export function SkillStepsCard({ steps, inProgress }: SkillStepsCardProps) {
                     'shrink-0 mt-0.5 inline-flex items-center justify-center size-4 rounded-full text-[10px] font-medium',
                     isActive
                       ? 'bg-violet-500 text-white'
-                      : isStopEarly
-                        ? 'bg-amber-100 dark:bg-amber-900/60 text-amber-600 dark:text-amber-300'
-                        : isResult
-                          ? 'bg-emerald-100 dark:bg-emerald-900/60 text-emerald-600 dark:text-emerald-300'
-                          : 'bg-violet-100 dark:bg-violet-900/60 text-violet-600 dark:text-violet-300',
+                      : isError
+                        ? 'bg-rose-100 dark:bg-rose-900/60 text-rose-600 dark:text-rose-300'
+                        : isStopEarly || isFallback
+                          ? 'bg-amber-100 dark:bg-amber-900/60 text-amber-600 dark:text-amber-300'
+                          : isResult
+                            ? 'bg-emerald-100 dark:bg-emerald-900/60 text-emerald-600 dark:text-emerald-300'
+                            : 'bg-violet-100 dark:bg-violet-900/60 text-violet-600 dark:text-violet-300',
                   )}
                 >
                   {isActive ? <Loader2 className="size-2.5 animate-spin" /> : idx + 1}
@@ -92,11 +101,13 @@ export function SkillStepsCard({ steps, inProgress }: SkillStepsCardProps) {
                   <div
                     className={cn(
                       'flex items-center gap-1 font-medium',
-                      isStopEarly
-                        ? 'text-amber-700 dark:text-amber-300'
-                        : isResult
-                          ? 'text-emerald-700 dark:text-emerald-300'
-                          : 'text-violet-700 dark:text-violet-300',
+                      isError
+                        ? 'text-rose-700 dark:text-rose-300'
+                        : isStopEarly || isFallback
+                          ? 'text-amber-700 dark:text-amber-300'
+                          : isResult
+                            ? 'text-emerald-700 dark:text-emerald-300'
+                            : 'text-violet-700 dark:text-violet-300',
                     )}
                   >
                     <Icon className="size-3 shrink-0" />

frontend-web/src/open-canvas/types/ai-writing.ts

@@ -20,6 +20,8 @@ export interface AIMaterial {
 //   select_skills：LLM 按相关度排序的候选
 //   invoke_skill：开始调用某个技能去检索
 //   skill_result：某个技能检索返回了 N 条素材
+//   skill_error：某个技能调用失败（超时/报错），将改用其他技能（容错）
+//   fallback：配置技能全部失败，回退到其他技能继续搜集（容错）
 //   stop_early：累计素材达到上限，停止后续技能
 export interface SkillSearchStep {
   type:
@@ -28,6 +30,8 @@ export interface SkillSearchStep {
     | "select_skills"
     | "invoke_skill"
     | "skill_result"
+    | "skill_error"
+    | "fallback"
     | "stop_early";
   message: string;
   skillNames?: string[];