refactor(markdown): Make module CLI-importable

Drop the mermaid import from the markdown module. The extension only emits <pre class="mermaid">, so initialize mermaid in the app entry instead. Use explicit .js specifiers plus a bundler extensionAlias so both the NodeNext CLI build and the web build resolve the sources.

src/markdown/code-block-yaml-tag.ts

@@ -1,6 +1,6 @@
 import type { MarkedExtension } from "marked";
 import yaml from "js-yaml";
-import { parseBlockAttrs } from "./block-attrs";
+import { parseBlockAttrs } from "./block-attrs.js";
 
 /**
  * YAML-defined tag blocks:

src/markdown/index.ts

@@ -1,12 +1,12 @@
 import { Marked, type MarkedExtension } from "marked";
 import { createDirectives, presetDirectiveConfigs } from "marked-directive";
 import markedAlert from "marked-alert";
-import markedMermaid from "./mermaid";
+import markedMermaid from "./mermaid.js";
 import { gfmHeadingId } from "marked-gfm-heading-id";
-import markedColumns from "./columns";
-import markedCodeBlockYamlTag from "./code-block-yaml-tag";
-import { iconDirective, setIconBase } from "./icon";
-import { cmdDirective } from "./cmd";
+import markedColumns from "./columns.js";
+import markedCodeBlockYamlTag from "./code-block-yaml-tag.js";
+import { iconDirective, setIconBase } from "./icon.js";
+import { cmdDirective } from "./cmd.js";
 
 // 使用 marked-directive 来支持指令语法
 const marked = new Marked()

src/markdown/mermaid.ts

@@ -1,9 +1,4 @@
 import type {MarkedExtension} from "marked";
-import mermaid from "mermaid";
-
-mermaid.initialize({
-    theme: 'dark'
-});
 
 export default function markedMermaid(): MarkedExtension {
     return {