feat(maps): 画布聚焦减负（聚焦层/详情浮层/汇总条/目标树收起/跨层摘要）— C 方案

- MapCanvas: 层聚焦与回全景联动；右栏停用改自绘可拖详情浮层；目标树默认收起+localStorage 持久化；底部跨层关系摘要条；聚焦态只绘聚焦层同层连线
- StrategyLayer: 层标题可点击聚焦并标「聚焦中」；非聚焦层压缩为 ≤48px 单行摘要（层名—达成率/目标数/mini 色条）
- MapSummaryBar: 汇总条压缩 ≤44px、5 项同排；窄屏无横向溢出
- MapEditBar: 新增「全景 / L1–L4」聚焦切换 chip（内联 SVG，无 emoji）
- 只读渲染层改动：不写 canvas_data / map_connections，无新增写链路调用

frontend/src/components/strategy-map/MapEditBar.vue

@@ -90,9 +90,32 @@
         回全景
       </el-button>
 
-      <el-button size="small" text @click="$emit('toggle-tree')">
+      <el-button size="small" text @click="$emit('toggle-tree')" :title="treeOpen ? '收起左侧目标树（画布全宽）' : '展开左侧目标树'">
         {{ treeOpen ? '收起目标树' : '展开目标树' }}
       </el-button>
+
+      <!-- C 方案：聚焦开关（全景 = 默认四层等宽） -->
+      <div class="eb-chips eb-focus" role="group" aria-label="聚焦层">
+        <button
+          type="button"
+          class="eb-chip"
+          :class="{ on: !focusLayer }"
+          title="四层全景（默认）"
+          @click="$emit('focus-layer', null)"
+        >全景</button>
+        <button
+          v-for="cfg in layerConfigs"
+          :key="'focus-' + cfg.key"
+          type="button"
+          class="eb-chip"
+          :class="{ on: focusLayer === cfg.key }"
+          :title="focusLayer === cfg.key ? '再次点击退出聚焦' : '聚焦' + cfg.label"
+          @click="$emit('focus-layer', focusLayer === cfg.key ? null : cfg.key)"
+        >
+          <span class="layer-dot" :style="{ background: cfg.color }"></span>
+          {{ cfg.short }}
+        </button>
+      </div>
     </div>
   </div>
 </template>
@@ -105,6 +128,8 @@ defineProps<{
   layerConfigs: { key: string; label: string; short: string; color: string }[]
   canUndo: boolean
   treeOpen: boolean
+  /** C 方案聚焦层：null = 四层全景 */
+  focusLayer?: string | null
 }>()
 
 const emit = defineEmits<{
@@ -117,6 +142,7 @@ const emit = defineEmits<{
   (e: 'fit'): void
   (e: 'toggle-tree'): void
   (e: 'completeness'): void
+  (e: 'focus-layer', key: string | null): void
 }>()
 
 const filterOptions: { value: 'all' | 'risk' | 'nodata'; label: string }[] = [