feat(editor): 面包屑超出父容器 80% 时折叠中间项并对单项打点

- 路径过长时仅保留首项 + ... + 末两项，避免横向溢出工作区
- 单项设置 max-width 并通过内部 span 显示省略号，悬浮 tooltip 展示完整名称
- 通过 ResizeObserver 监听父容器宽度变化实时重测

Co-authored-by: Cursor <cursoragent@cursor.com>

packages/editor/src/layouts/workspace/Breadcrumb.vue

@@ -1,17 +1,22 @@
 <template>
-  <div v-if="nodes.length === 1" class="m-editor-breadcrumb">
-    <template v-for="(item, index) in path" :key="item.id">
-      <TMagicButton link :disabled="item.id === node?.id" @click="select(item)">{{ item.name }}</TMagicButton
-      ><span v-if="index < path.length - 1">/</span>
+  <div v-if="nodes.length === 1" ref="containerRef" class="m-editor-breadcrumb">
+    <template v-for="(item, index) in displayPath" :key="item.isEllipsis ? `ellipsis-${index}` : item.id">
+      <span v-if="item.isEllipsis" class="m-editor-breadcrumb-ellipsis">...</span>
+      <TMagicTooltip v-else :content="item.name" placement="top" :show-after="500">
+        <TMagicButton class="m-editor-breadcrumb-item" link :disabled="item.id === node?.id" @click="select(item)">{{
+          item.name
+        }}</TMagicButton>
+      </TMagicTooltip>
+      <span v-if="index < displayPath.length - 1" class="m-editor-breadcrumb-separator">/</span>
     </template>
   </div>
 </template>
 
 <script setup lang="ts">
-import { computed } from 'vue';
+import { computed, nextTick, onBeforeUnmount, onMounted, ref, watch } from 'vue';
 
 import type { MNode } from '@tmagic/core';
-import { TMagicButton } from '@tmagic/design';
+import { TMagicButton, TMagicTooltip } from '@tmagic/design';
 import { getNodePath } from '@tmagic/utils';
 
 import { useServices } from '@editor/hooks/use-services';
@@ -20,6 +25,8 @@ defineOptions({
   name: 'MEditorBreadcrumb',
 });
 
+type DisplayItem = (MNode & { isEllipsis?: false }) | { isEllipsis: true; id: string; name: string };
+
 const { editorService } = useServices();
 
 const node = computed(() => editorService.get('node'));
@@ -27,6 +34,80 @@ const nodes = computed(() => editorService.get('nodes'));
 const root = computed(() => editorService.get('root'));
 const path = computed(() => getNodePath(node.value?.id || '', root.value?.items || []));
 
+const containerRef = ref<HTMLElement | null>(null);
+// 当面包屑宽度超过父元素宽度的阈值时折叠
+const COLLAPSE_RATIO = 0.8;
+const collapsed = ref(false);
+
+const displayPath = computed<DisplayItem[]>(() => {
+  const list = path.value;
+  // 折叠后视觉元素数（first + ... + last2 = 4 个），所以只有路径 > 3 时折叠才能减少占位
+  if (!collapsed.value || list.length <= 3) {
+    return list as DisplayItem[];
+  }
+  return [
+    list[0],
+    { isEllipsis: true, id: '__ellipsis__', name: '...' },
+    list[list.length - 2],
+    list[list.length - 1],
+  ] as DisplayItem[];
+});
+
+const measureOverflow = async () => {
+  // 先恢复完整渲染再测量，避免折叠后误判
+  if (collapsed.value) {
+    collapsed.value = false;
+    await nextTick();
+  }
+  const el = containerRef.value;
+  const parent = el?.parentElement;
+  if (!el || !parent) return;
+  // scrollWidth 取内容自然宽度（不受自身 max-width 影响），与父容器宽度做比例判断
+  const contentWidth = el.scrollWidth;
+  const parentWidth = parent.clientWidth;
+  if (parentWidth <= 0) return;
+  collapsed.value = contentWidth > parentWidth * COLLAPSE_RATIO;
+};
+
+let resizeObserver: ResizeObserver | null = null;
+
+const observe = () => {
+  resizeObserver?.disconnect();
+  const el = containerRef.value;
+  if (!el || typeof ResizeObserver === 'undefined') return;
+  resizeObserver = new ResizeObserver(() => {
+    measureOverflow();
+  });
+  resizeObserver.observe(el);
+  if (el.parentElement) {
+    resizeObserver.observe(el.parentElement);
+  }
+};
+
+onMounted(() => {
+  observe();
+  measureOverflow();
+});
+
+onBeforeUnmount(() => {
+  resizeObserver?.disconnect();
+  resizeObserver = null;
+});
+
+watch(
+  () => nodes.value.length,
+  async () => {
+    await nextTick();
+    observe();
+    measureOverflow();
+  },
+);
+
+watch(path, async () => {
+  await nextTick();
+  measureOverflow();
+});
+
 const select = async (node: MNode) => {
   await editorService.select(node);
   editorService.get('stage')?.select(node.id);

packages/editor/src/theme/breadcrumb.scss

@@ -3,4 +3,28 @@
   left: 5px;
   top: 5px;
   z-index: 10;
+  display: flex;
+  align-items: center;
+  white-space: nowrap;
+
+  .m-editor-breadcrumb-item {
+    max-width: 100px;
+    min-width: 0;
+    overflow: hidden;
+
+    // Element Plus button 内部文本节点
+    > span {
+      display: block;
+      max-width: 100%;
+      overflow: hidden;
+      text-overflow: ellipsis;
+      white-space: nowrap;
+    }
+  }
+
+  .m-editor-breadcrumb-separator,
+  .m-editor-breadcrumb-ellipsis {
+    margin: 0 4px;
+    flex-shrink: 0;
+  }
 }