perf(门店选择): 门店明细移出页面 data，修复首屏卡顿

门店接口 /shop/merchant/groupByChain 一次返回 8105 家门店（约 1.1MB）。
此前把门店明细原样放进页面 data，data 树膨胀到 1118KB，导致此后每次
setData 都要重新 diff/序列化整棵树——即使载荷只有 1 个字段，耗时也从
约 490ms 涨到约 1000ms，首屏因此多花约 3.5s。

改为把明细挂在实例属性 merchantStore 上（不进页面 data），
merchantChainList 只保留 {id, text, merchantCount} 骨架，
新增 getMerchantsByChainId() / getVisibleMerchants() 按需取数。

涉及页面：
- packageUser/self-report/create.vue
- packageUser/chronic/index.vue
- pages/task/detail.vue
- pages/share/create.vue
- pages/share/index.vue
- pages/audit/components/AuditShareItem.vue

实测（微信开发者工具自动化）：
- 页面 data 门店明细 1118KB -> 1KB
- 单字段 setData 998ms -> 10~53ms
- self-report/create 首屏 9055ms -> 5341ms
- 门店 picker 选项数不变（大参林 2700 项），搜索与选中回填均正常

pages/audit/components/AuditShareItem.vue

@@ -370,26 +370,20 @@ export default {
     editMerchantChainOptions() {
       const list = Array.isArray(this.merchantChainList) ? this.merchantChainList : []
       const keyword = (this.editMerchantSearchKeyword || '').trim()
-      if (!keyword) return list.length ? list : [{id: '', text: '暂无连锁', merchants: []}]
+      if (!keyword) return list.length ? list : [{id: '', text: '暂无连锁', merchantCount: 0}]
       const filtered = list
         .map(chain => {
-          const merchants = Array.isArray(chain.merchants) ? chain.merchants : []
-          const chainMatch = (chain.text || '').includes(keyword)
-          if (chainMatch) return {...chain}
-          const matchedMerchants = merchants.filter(merchant => (merchant.text || '').includes(keyword))
-          if (!matchedMerchants.length) return null
-          return {
-            ...chain,
-            merchants: matchedMerchants
-          }
+          const visible = this.getVisibleMerchants(chain)
+          if (!visible.length) return null
+          return Object.assign({}, chain, {merchantCount: visible.length})
         })
         .filter(Boolean)
-      return filtered.length ? filtered : [{id: '', text: '无匹配连锁', merchants: []}]
+      return filtered.length ? filtered : [{id: '', text: '无匹配连锁', merchantCount: 0}]
     },
     editMerchantStoreOptions() {
       const chainIndex = Number(this.editMerchantPickerValue[0] || 0)
       const currentChain = this.editMerchantChainOptions[chainIndex] || this.editMerchantChainOptions[0] || {}
-      const merchants = Array.isArray(currentChain.merchants) ? currentChain.merchants : []
+      const merchants = this.getVisibleMerchants(currentChain)
       return merchants.length ? merchants : [{id: '', text: '无门店'}]
     },
     editMerchantPickerIndexes() {
@@ -398,12 +392,12 @@ export default {
       let chainIndex = chainList.findIndex(item => item.id === this.editForm.chainId)
       if (chainIndex < 0 && this.editForm.merchantId) {
         chainIndex = chainList.findIndex(item => {
-          const merchants = Array.isArray(item.merchants) ? item.merchants : []
+          const merchants = this.getMerchantsByChainId(item && item.id)
           return merchants.some(merchant => merchant.id === this.editForm.merchantId)
         })
       }
       if (chainIndex < 0) chainIndex = 0
-      const merchants = Array.isArray(chainList[chainIndex].merchants) ? chainList[chainIndex].merchants : []
+      const merchants = this.getMerchantsByChainId(chainList[chainIndex] && chainList[chainIndex].id)
       let merchantIndex = merchants.findIndex(item => item.id === this.editForm.merchantId)
       if (merchantIndex < 0) merchantIndex = 0
       return [chainIndex, merchantIndex]
@@ -470,10 +464,28 @@ export default {
       this.editMerchantPickerValue = [0, 0]
     }
   },
+  created() {
+    // 门店明细挂实例上而非 data：data 里的一切都会进页面 data 树并被 setData 序列化
+    this.merchantStore = []
+  },
   beforeDestroy() {
     this.clearGoodsCodeTimers()
   },
   methods: {
+    // 门店明细只存在实例的 merchantStore 上（不进页面 data），按连锁 id 取
+    getMerchantsByChainId(chainId) {
+      const store = Array.isArray(this.merchantStore) ? this.merchantStore : []
+      const chain = store.find(item => String(item.id) === String(chainId))
+      return chain && Array.isArray(chain.merchants) ? chain.merchants : []
+    },
+    // 搜索关键词命中的门店：连锁名命中则整列保留，否则按门店名过滤
+    getVisibleMerchants(chain) {
+      const merchants = this.getMerchantsByChainId(chain && chain.id)
+      const keyword = (this.editMerchantSearchKeyword || '').trim()
+      if (!keyword) return merchants
+      if ((chain.text || '').includes(keyword)) return merchants
+      return merchants.filter(merchant => (merchant.text || '').includes(keyword))
+    },
     async toggleDetailExpanded() {
       const nextExpanded = !this.detailExpanded
       this.detailExpanded = nextExpanded
@@ -1048,11 +1060,12 @@ export default {
       try {
         const {data} = await merchantGroupByChainReq({})
         const list = this.unwrapNestedList(data)
-        this.merchantChainList = list
+        const chains = list
           .map((item, index) => this.normalizeMerchantChain(item, index))
           .filter(item => Array.isArray(item.merchants) && item.merchants.length > 0)
+        this.setMerchantChains(chains)
       } catch (error) {
-        this.merchantChainList = []
+        this.setMerchantChains([])
         uni.showToast({
           title: '门店列表获取失败',
           icon: 'none'
@@ -1061,6 +1074,22 @@ export default {
         this.merchantLoading = false
       }
     },
+    // 门店明细（全量可达 8000+ 条）只放在实例上，不进页面 data。
+    // 一旦放进 data，页面 data 树会膨胀到 1MB+，此后每次 setData 都要重新
+    // diff/序列化整棵树，连只含一个字段的 setData 也会从 ~490ms 涨到 ~1000ms。
+    setMerchantChains(chains) {
+      const list = Array.isArray(chains) ? chains : []
+      this.merchantStore = list.map(chain => ({
+        id: chain.id,
+        text: chain.text,
+        merchants: Array.isArray(chain.merchants) ? chain.merchants : []
+      }))
+      this.merchantChainList = this.merchantStore.map(chain => ({
+        id: chain.id,
+        text: chain.text,
+        merchantCount: chain.merchants.length
+      }))
+    },
     async openEditMerchantPicker() {
       if (!this.merchantChainList || this.merchantChainList.length === 0) {
         await this.getMerchantList()
@@ -1075,7 +1104,7 @@ export default {
       const chainIndex = Number(this.editMerchantPickerValue[0] || 0)
       const merchantIndex = Number(this.editMerchantPickerValue[1] || 0)
       const chain = this.editMerchantChainOptions[chainIndex] || null
-      const merchants = chain && Array.isArray(chain.merchants) ? chain.merchants : []
+      const merchants = this.getVisibleMerchants(chain)
       const selected = merchants[merchantIndex]
       if (!selected || selected.id === '' || selected.id === null || selected.id === undefined) {
         return
@@ -1096,7 +1125,7 @@ export default {
       if (!Number.isFinite(chainIndex) || chainIndex < 0) chainIndex = 0
       if (!Number.isFinite(merchantIndex) || merchantIndex < 0) merchantIndex = 0
       const chain = this.editMerchantChainOptions[chainIndex] || this.editMerchantChainOptions[0] || {}
-      const merchants = Array.isArray(chain.merchants) ? chain.merchants : []
+      const merchants = this.getVisibleMerchants(chain)
       if (!merchants.length) {
         merchantIndex = 0
       } else if (chainIndex !== currentChainIndex || merchantIndex > merchants.length - 1) {