feat: 增加 ECharts 渲染与预览交互增强

- 新增可复用的 markdown-echarts 工作区，支持安全的 YAML 围栏、默认值、语义校验、错误占位和 SVG 渲染
- 将 ECharts 接入统一 Markdown、快速预览、精确预览与 PDF 链路，并复用 Mermaid 的不可跨页和超高图单页适配策略
- 默认示例加入 ECharts，增加源文本折叠、顶部文档状态、页码输入跳转与滚动同步
- 快速预览改用外层容器滚动，使滚动条与精确预览统一贴在预览区域右侧，并兼容显示缩放
- 完善 Docker 工作区复制、可配置 Compose 镜像、测试覆盖和进度文档

packages/markdown-echarts/package.json

@@ -0,0 +1,46 @@
+{
+  "name": "@md-to-pdf/markdown-echarts",
+  "version": "0.1.0",
+  "private": true,
+  "type": "module",
+  "main": "./dist/index.js",
+  "types": "./dist/index.d.ts",
+  "exports": {
+    ".": {
+      "types": "./dist/index.d.ts",
+      "import": "./dist/index.js"
+    },
+    "./browser": {
+      "types": "./dist/browser.d.ts",
+      "import": "./dist/browser.js"
+    },
+    "./styles.css": {
+      "default": "./styles/echarts.css"
+    }
+  },
+  "files": [
+    "dist",
+    "styles"
+  ],
+  "scripts": {
+    "dev": "tsc -p tsconfig.json --watch --preserveWatchOutput",
+    "build": "tsc -p tsconfig.json",
+    "test": "vitest run",
+    "typecheck": "tsc -p tsconfig.json --noEmit --pretty false"
+  },
+  "dependencies": {
+    "yaml": "^2.8.1",
+    "zod": "^4.1.13"
+  },
+  "peerDependencies": {
+    "echarts": "^6.1.0",
+    "markdown-it": "^14.3.0"
+  },
+  "devDependencies": {
+    "@types/markdown-it": "^14.1.2",
+    "echarts": "6.1.0",
+    "happy-dom": "^20.11.1",
+    "markdown-it": "^14.3.0",
+    "vitest": "^4.1.10"
+  }
+}