test(markdown): cover attrs/anchor plugin order independence

attrs registers its core rule at a fixed position (before linkify)
while anchor pushes to the end of the chain, so user-defined ids from
curly attributes win regardless of registration order. Remove the
comment that claimed the order matters.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

__tests__/unit/node/markdown/markdown.test.ts

@@ -1,3 +1,6 @@
+import { anchor as anchorPlugin } from '@mdit/plugin-anchor'
+import attrsPlugin from 'markdown-it-attrs'
+import { MarkdownItAsync } from 'markdown-it-async'
 import {
   createMarkdownRenderer,
   disposeMdItInstance,
@@ -110,4 +113,20 @@ describe('node/markdown/markdown', () => {
       )
     })
   })
+
+  // attrs applies at a fixed position in the core chain (before linkify),
+  // while anchor pushes to its end, so anchor always sees user-defined ids
+  // no matter which plugin is registered first
+  test('anchor respects ids from attrs regardless of plugin order', async () => {
+    for (const plugins of [
+      [attrsPlugin, anchorPlugin],
+      [anchorPlugin, attrsPlugin]
+    ] as const) {
+      const md = new MarkdownItAsync()
+      for (const plugin of plugins) md.use(plugin)
+      expect(await md.renderAsync('## Title {#custom-id}')).toContain(
+        'id="custom-id"'
+      )
+    }
+  })
 })

src/node/markdown/markdown.ts

@@ -361,8 +361,6 @@ export async function createMarkdownRenderer(
     mditCjkFriendly(md)
   }
   if (options.anchor !== false) {
-    // must be applied after attrs so that user-defined ids from curly
-    // attributes take precedence over slugified ones
     anchorPlugin(md, {
       slugify,
       getTokensText: (tokens) => {