fix: AI预测无反馈 + 增加推理建议展示

- useAIPredict 增加 markdown 代码块剥离逻辑
- Prompt 模板要求返回纯 JSON
- 可视化编辑器显示预测错误信息
- 展示 AI 推理建议（建议如何优化配方）

frontend/src/components/FormulaVisualEditor.tsx

@@ -121,7 +121,7 @@ export default function FormulaVisualEditor({ phases: initialPhases, onSave }: P
     } finally { setSaving(false) }
   }
 
-  const { prediction, loading: predicting, predict } = useAIPredict()
+  const { prediction, loading: predicting, error: predictError, predict } = useAIPredict()
 
   const handlePredict = () => {
     predict(allIngredients.map(i => ({
@@ -169,6 +169,7 @@ export default function FormulaVisualEditor({ phases: initialPhases, onSave }: P
             {predicting ? <Loader2 size={14} className="animate-spin" /> : <Sparkles size={14} />}
             {predicting ? '预测中...' : 'AI 预测指标'}
           </button>
+          {predictError && <span className="text-xs text-red-500">{predictError}</span>}
         </div>
 
         {hasPrediction && (
@@ -188,6 +189,13 @@ export default function FormulaVisualEditor({ phases: initialPhases, onSave }: P
           </div>
         )}
 
+        {hasPrediction && prediction!.reasoning && (
+          <div className="mb-4 rounded-lg border border-blue-200 bg-blue-50 p-3">
+            <p className="text-xs font-medium text-blue-600 mb-1">💡 AI 建议</p>
+            <p className="text-sm text-blue-800">{prediction!.reasoning}</p>
+          </div>
+        )}
+
         {hasPrediction && (
           <div className="mb-4 grid grid-cols-1 gap-4 lg:grid-cols-2">
             <div className="rounded-lg border p-3">

frontend/src/hooks/useAIPredict.ts

@@ -56,7 +56,8 @@ export function useAIPredict() {
           if (line.startsWith('data: ')) {
             const data = JSON.parse(line.slice(6)) as { type: string; content: string }
             if (data.type === 'result') {
-              const parsed = JSON.parse(data.content) as PredictionResult
+              const clean = data.content.replace(/```(?:json)?\s*/g, '').replace(/```/g, '').trim()
+              const parsed = JSON.parse(clean) as PredictionResult
               setPrediction(parsed)
             } else if (data.type === 'error') {
               setError('AI 预测失败')