fix(diy): 草稿持久化 + 进入工作台即设计中 + 编辑页空态兜底

修正工作流批次①（问题 2+3+4）：
- 问题2: 贴纸变化防抖 800ms 落缓存+服务端静默同步，
  useDidHide/卸载前强制 flush；中途退出不再丢布局
- 问题3: 进入工作台（新建/继续）即 PATCH designing（SUBMITTED），
  取代原「确认完成才提交」触发点
- 问题4: 草稿实时写缓存后贴纸编辑页始终能读到 stickers；
  另加 notFound 空态（未找到贴纸提示 + 返回工作台），
  handleEditSticker 跳转前 flushDraft 关闭防抖竞态窗口

Co-Authored-By: Claude <noreply@anthropic.com>

src/pages/diy/index.tsx

@@ -1,6 +1,6 @@
 import { View, Text, Image } from '@tarojs/components'
 import Taro from '@tarojs/taro'
-import { useState, useEffect } from 'react'
+import { useState, useEffect, useRef } from 'react'
 import './index.scss'
 import { getProductById } from '../../utils/productConfig'
 import { getDesignList, setDesignList, updateDesign, type DesignItem, type StickerItem } from '../../utils/store'
@@ -27,7 +27,7 @@ export default function DIYPage() {
   const [previewMode, setPreviewMode] = useState(false)
   const [hasOverlap, setHasOverlap] = useState(false)
 
-  /** 进入 DIY 即创建清单条目：服务端创建（DRAFT，阶段0 决策#6），失败降级本地 */
+  /** 进入 DIY 即创建清单条目，并推进到「设计中」（问题3 修正：进入工作台即 SUBMITTED），失败降级本地 */
   const createDesignEntry = (product: { id: string; name: string; price: number; icon: string }, count: number) => {
     createDesign({
       productId: product.id,
@@ -38,6 +38,13 @@ export default function DIYPage() {
       .then(item => {
         setDesignList([item, ...getDesignList()]) // 回写缓存，checkout 等页面仍读缓存
         setDesignId(item.id)
+        return updateDesignApi(item.id, { status: 'designing' })
+          .then(updated => {
+            setDesignList(getDesignList().map(d => d.id === item.id ? { ...d, status: updated.status } : d))
+          })
+          .catch(() => {
+            setDesignList(getDesignList().map(d => d.id === item.id ? { ...d, status: 'designing' as const } : d))
+          })
       })
       .catch(() => {
         const newDesign: DesignItem = {
@@ -47,7 +54,7 @@ export default function DIYPage() {
           productIcon: product.icon,
           unitPrice: product.price,
           count,
-          status: 'undesigned',
+          status: 'designing',
           createdAt: new Date().toISOString().slice(0, 10)
         }
         setDesignList([...getDesignList(), newDesign])
@@ -97,6 +104,12 @@ export default function DIYPage() {
           }
           setStickers([s])
         }
+
+        // 问题3 修正：继续设计同样进入「设计中」状态（单向状态机，undesigned → designing）
+        if (design.status === 'undesigned') {
+          updateDesign(dId, { status: 'designing' })
+          updateDesignApi(dId, { status: 'designing' }).catch(() => {})
+        }
       }
       return
     }
@@ -111,6 +124,51 @@ export default function DIYPage() {
     }
   }, [])
 
+  // ---------- 草稿持久化（修正工作流 问题2）----------
+  // 贴纸变化防抖 800ms：本地缓存即时同步 + 服务端静默同步；不推状态（SUBMITTED 只由显式动作触发）
+  const draftTimerRef = useRef<ReturnType<typeof setTimeout> | null>(null)
+  const latestRef = useRef({ designId: '', quantity: 1, category: null as any, stickers: [] as StickerItem[] })
+  latestRef.current = { designId, quantity, category, stickers }
+
+  const saveDraft = () => {
+    const { designId: dId, quantity: qty, category: cat, stickers: st } = latestRef.current
+    if (!dId || !cat) return
+    // WCD 红线：基于缓存中服务端最新 designData 合并（保留 wordcloud 分组），只覆盖本页编辑字段
+    const cached = getDesignList().find(d => d.id === dId)
+    const designData = {
+      ...(cached && cached.designData ? cached.designData : {}),
+      version: 1 as const,
+      category: { id: cat.id, mask: cat.mask, ...(cat.tone ? { tone: cat.tone } : {}) },
+      stickers: st
+    }
+    updateDesign(dId, { designData }) // 本地缓存即时同步（问题4：贴纸编辑页从这里读取）
+    updateDesignApi(dId, {
+      item: { productId: cat.id, productName: cat.name, unitPrice: cat.price, count: qty, designData }
+    }).catch(() => {}) // 草稿静默降级：失败仅落缓存
+  }
+
+  const flushDraft = () => {
+    if (draftTimerRef.current) {
+      clearTimeout(draftTimerRef.current)
+      draftTimerRef.current = null
+    }
+    saveDraft()
+  }
+
+  // 隐藏页面（切后台/跳转）时强制落盘，防止防抖窗口内的改动丢失
+  Taro.useDidHide(flushDraft)
+  // 卸载时同样落盘
+  useEffect(() => flushDraft, [])
+  // eslint-disable-next-line react-hooks/exhaustive-deps
+
+  const skipDraftRef = useRef(true)
+  useEffect(() => {
+    if (skipDraftRef.current) { skipDraftRef.current = false; return }
+    if (draftTimerRef.current) clearTimeout(draftTimerRef.current)
+    draftTimerRef.current = setTimeout(saveDraft, 800)
+    // eslint-disable-next-line react-hooks/exhaustive-deps
+  }, [stickers])
+
   // 矩形碰撞检测
   const checkOverlap = (list: StickerItem[]) => {
     const newList = list.map(s => ({ ...s, isOverlapping: false }))
@@ -217,6 +275,7 @@ export default function DIYPage() {
 
   const handleEditSticker = () => {
     if (!activeStickerId || !designId) return
+    flushDraft() // 问题4：跳编辑页前清掉防抖窗口，缓存里保证有最新贴纸
     Taro.navigateTo({
       url: `/pages/diy/stickerEdit/index?designId=${designId}&stickerId=${activeStickerId}`
     })