fix: 改用 importmap + esm.sh 解决 CodeMirror 多实例冲突

- 将 import 改回 bare specifier，通过 importmap 指向 esm.sh
- esm.sh 在同一构建上下文中能识别共享依赖，确保 @codemirror/state 单例
- 消除 "Unrecognized extension value" instanceof 检查错误

internal/middleware/security.go

@@ -10,14 +10,14 @@ func SecurityHeaders() gin.HandlerFunc {
 	return func(c *gin.Context) {
 		// Content-Security-Policy
 		// script-src: 本站 + esm.sh CDN (CodeMirror 6 ESM 模块)
-		// connect-src: 本站 (Markdown 预览等 fetch 请求)
+		// connect-src: 本站 + esm.sh (source map 请求)
 		// img-src: 本站 + data: URI (头像裁切) + blob: (粘贴图片)
 		c.Header("Content-Security-Policy",
 			"default-src 'self'; "+
 				"script-src 'self' 'unsafe-inline' https://esm.sh; "+
 				"style-src 'self' 'unsafe-inline'; "+
 				"img-src 'self' data: blob:; "+
-				"connect-src 'self'")
+				"connect-src 'self' https://esm.sh")
 
 		// 禁止 MIME 类型嗅探
 		c.Header("X-Content-Type-Options", "nosniff")

templates/MetaLab-2026/html/posts/new.html

@@ -124,6 +124,27 @@
 
 {{template "layout/footer.html" .}}
 
-{{/* CodeMirror 6 (MIT License, via esm.sh bundle) */}}
+{{/* CodeMirror 6 importmap — 所有 @codemirror/@lezer 指向 esm.sh 同一构建树，共享依赖单例 */}}
+<script type="importmap">
+{
+    "imports": {
+        "@codemirror/state":          "https://esm.sh/@codemirror/state@6.5.2",
+        "@codemirror/view":           "https://esm.sh/@codemirror/view@6.36.4",
+        "@codemirror/commands":       "https://esm.sh/@codemirror/commands@6.8.1",
+        "@codemirror/language":       "https://esm.sh/@codemirror/language@6.11.0",
+        "@codemirror/lang-markdown":  "https://esm.sh/@codemirror/lang-markdown@6.3.2",
+        "@codemirror/language-data":  "https://esm.sh/@codemirror/language-data@6.5.1",
+        "@codemirror/autocomplete":   "https://esm.sh/@codemirror/autocomplete@6.18.6",
+        "@codemirror/search":         "https://esm.sh/@codemirror/search@6.5.10",
+        "@lezer/common":              "https://esm.sh/@lezer/common@1.2.3",
+        "@lezer/highlight":           "https://esm.sh/@lezer/highlight@1.2.1",
+        "@lezer/lr":                  "https://esm.sh/@lezer/lr@1.4.2",
+        "@lezer/markdown":            "https://esm.sh/@lezer/markdown@1.4.0",
+        "crelt":                      "https://esm.sh/crelt@1.0.6",
+        "style-mod":                  "https://esm.sh/style-mod@4.1.2",
+        "w3c-keyname":                "https://esm.sh/w3c-keyname@2.2.8"
+    }
+}
+</script>
 <script src="/static/js/common.js"></script>
 <script type="module" src="/static/js/editor.js"></script>

templates/MetaLab-2026/static/js/editor.js

@@ -1,28 +1,17 @@
 /**
  * MetaLab Markdown Editor — CodeMirror 6 版
  *
- * 功能：
+ * 依赖通过 importmap 指向 esm.sh，所有 @codemirror/@lezer 共享同一构建树，
- * - CodeMirror 6 编辑器，Markdown 语法高亮
+ * 避免多实例导致的 "Unrecognized extension value" 错误。
- * - 工具栏：加粗/斜体/删除线/行内代码/标题/链接/图片/引用/代码块/列表/表格/分割线
- * - 快捷键：Ctrl+B/I/K/` Shift+I Tab Shift+Tab Ctrl+S Ctrl+Shift+P F11
- * - 粘贴图片 / 拖拽上传 / 进度反馈
- * - 分屏实时预览（Ctrl+Shift+P 切换）
- * - 代码块语言下拉选择器
- * - 自动保存草稿（localStorage + 后端）
- * - 字数/行数/阅读时间统计
- * - 全屏编辑模式（F11）
- * - 滚动同步（分屏模式下）
- *
- * CodeMirror 6 通过 esm.sh bundle 加载，所有依赖自动解析。
  */
-import { EditorState } from 'https://esm.sh/@codemirror/state@6.5.2';
+import { EditorState } from '@codemirror/state';
-import { EditorView, keymap, lineNumbers, highlightActiveLine, drawSelection } from 'https://esm.sh/@codemirror/view@6.36.4';
+import { EditorView, keymap, lineNumbers, highlightActiveLine, drawSelection } from '@codemirror/view';
-import { defaultKeymap, history, historyKeymap, indentWithTab } from 'https://esm.sh/@codemirror/commands@6.8.1';
+import { defaultKeymap, history, historyKeymap, indentWithTab } from '@codemirror/commands';
-import { markdown, markdownLanguage } from 'https://esm.sh/@codemirror/lang-markdown@6.3.2';
+import { markdown, markdownLanguage } from '@codemirror/lang-markdown';
-import { languages } from 'https://esm.sh/@codemirror/language-data@6.5.1';
+import { languages } from '@codemirror/language-data';
-import { syntaxHighlighting, defaultHighlightStyle } from 'https://esm.sh/@codemirror/language@6.11.0';
+import { syntaxHighlighting, defaultHighlightStyle } from '@codemirror/language';
-import { searchKeymap } from 'https://esm.sh/@codemirror/search@6.5.10';
+import { searchKeymap } from '@codemirror/search';
-import { autocompletion } from 'https://esm.sh/@codemirror/autocomplete@6.18.6';
+import { autocompletion } from '@codemirror/autocomplete';
 
 /* ================================================================
    DOM 引用