feat(markdown): 只读内容支持 Markdown 渲染

- 新增 MarkdownRenderer.vue 组件，基于 marked 解析 GFM
- 学习残片/报告历史列表：纯文本 {{ }} 替换为 MarkdownRenderer
- ReviewDetail.vue content-body：p 标签逐行渲染替换为 MarkdownRenderer
- 结束会话总结框：增加「编辑/预览」切换，预览模式实时渲染 markdown
- 学习预期展示也改为 MarkdownRenderer

package-lock.json

@@ -12,6 +12,7 @@
         "axios": "^1.7.7",
         "css-loader": "^7.1.2",
         "element-plus": "^2.8.7",
+        "marked": "^18.0.5",
         "mind-elixir": "^5.13.0",
         "normalize": "^0.3.1",
         "normalize.css": "^8.0.1",
@@ -2683,6 +2684,17 @@
         "@jridgewell/sourcemap-codec": "^1.5.0"
       }
     },
+    "node_modules/marked": {
+      "version": "18.0.5",
+      "resolved": "https://registry.npmmirror.com/marked/-/marked-18.0.5.tgz",
+      "integrity": "sha512-S6GcvALHg6K4ohtu4E7x0a1AqhAjp6cV8KhLSyN9qVapnzJkusVBxZRcIU9AeYsbe6P1hKDusSbEOzGyyuce6w==",
+      "bin": {
+        "marked": "bin/marked.js"
+      },
+      "engines": {
+        "node": ">= 20"
+      }
+    },
     "node_modules/memoize-one": {
       "version": "6.0.0",
       "resolved": "https://registry.npmmirror.com/memoize-one/-/memoize-one-6.0.0.tgz",
@@ -6453,6 +6465,11 @@
         "@jridgewell/sourcemap-codec": "^1.5.0"
       }
     },
+    "marked": {
+      "version": "18.0.5",
+      "resolved": "https://registry.npmmirror.com/marked/-/marked-18.0.5.tgz",
+      "integrity": "sha512-S6GcvALHg6K4ohtu4E7x0a1AqhAjp6cV8KhLSyN9qVapnzJkusVBxZRcIU9AeYsbe6P1hKDusSbEOzGyyuce6w=="
+    },
     "memoize-one": {
       "version": "6.0.0",
       "resolved": "https://registry.npmmirror.com/memoize-one/-/memoize-one-6.0.0.tgz",