GitHub-style <details> block content is parsed outside the details element

[pynickle]

Environment

• Operating System: Windows 11
• Node Version: v24.16.0
• Package Manager: bun@1.3.14
• Comark Version: 0.4.0
• Framework: Vue / Nuxt

Comark Version

v0.4.0

Reproduction

import { parse } from 'comark'

const markdown = `<details>
<summary>Original summary in English</summary>

xxx
</details>`

console.log(JSON.stringify((await parse(markdown)).nodes, null, 2))

Actual output:

[
  [
    "details",
    {
      "$": {
        "html": 1,
        "block": 1
      }
    },
    [
      "summary",
      {
        "$": {
          "html": 1,
          "block": 1
        }
      },
      "Original summary in English"
    ]
  ],
  [
    "p",
    {},
    "xxx"
  ]
]

Expected output should keep xxx inside the details node, for example:

[
  [
    "details",
    {
      "$": {
        "html": 1,
        "block": 1
      }
    },
    [
      "summary",
      {
        "$": {
          "html": 1,
          "block": 1
        }
      },
      "Original summary in English"
    ],
    [
      "p",
      {},
      "xxx"
    ]
  ]
]

Description

GitHub-style collapsed sections using <details> / <summary> are not parsed correctly when the <summary> line is followed by a blank line.

Input:

<details>
<summary>Original summary in English</summary>

xxx
</details>

In GitHub Markdown, the body content remains inside the <details> block and is hidden until expanded. GitHub's Markdown API renders this as:

Original summary in English

xxx

Comark currently parses xxx as a sibling after the details node. Framework renderers then faithfully render the AST as:

Original summary in English

xxx

This breaks GitHub-compatible rendering for collapsed sections.

The issue appears related to raw HTML block handling. <details> / <summary> are treated as block HTML, and the blank line after <summary> appears to terminate the HTML block before is reached.

Additional context

No response

Logs

[c-harding]

It seems like all type-6 blocks (HTML block elements) containing blank lines parse incorrectly according to the specification:

compare commonmark demo (see the HTML tab) with the same code in the comark editor.

<details>
<summary>Original summary in English</summary>

xxx
</details>

<div class=foo">

*Markdown*

</div>

The correct result according to the reference implementation:

<details>
<summary>Original summary in English</summary>
<p>xxx</p>
</details>
<div class=foo">
<p><em>Markdown</em></p>
</div>