<details open> in safe-output bodies renders as escaped text since v1.0.1 #75115

<details open> in safe-output bodies renders as escaped text since v1.0.1

Analysis

Since #72415 (v1.0.1), create_issue, add_comment and the other publishers parse agent bodies with parseReportMarkdown. The parser only recognizes a literal <details>, so <details open> falls through to paragraphs, and the output shows <details open>…</details> as text. In v1.0.0 the body only went through sanitizeContent, which deliberately keeps open (sanitize_content.test.cjs:870).

Repro:

<details open>
<summary>Open</summary>

body

</details>

This currently renders as escaped text. A plain <details> renders correctly.

Implementation plan

1. actions/setup/js/report_markdown.cjs
   • In the block-start regex (around L401), accept <details(?:\s+open)?>.
   • In the two details branches (around L505 and L508), accept the same form and set open: true.
2. actions/setup/js/report_ast.cjs
   • Add open?: boolean to the details typedef (L23).
   • Carry open through when the details node is normalized (around L405).
   • Have the renderer (around L671) emit <details open> when open is set.
3. Tests: add cases to report_html_fidelity.test.cjs for both the inline (<details open><summary>) and two-line forms. Assert that the tree has open: true and that rendering round-trips. Keep <details> with any other attribute rejected as it is today.
4. Add a patch changeset and run make agent-finish.

Acceptance: <details open> in an agent body publishes as an expanded details block, and existing <details> output is unchanged.