fix: use 6-backtick fences in summaries to prevent escaping breakage

[Copilot]

Step summaries broke when safe-output body content (issue/PR bodies, error details) contained triple-backtick code fences — the inner ``` prematurely closed the outer fence, leaking raw content including XML-like tags into the rendered summary.

Changes

• safe_output_summary.cjs: Change 3→6 backtick fences for body preview and message details JSON
• log_parser_shared.cjs: Change 3→6 backtick fences for safe-outputs body preview
• safe_output_summary.test.cjs: Add tests for body content containing triple backticks

Before / After

// Before — breaks if bodyPreview contains ```
summary += `**Body Preview:**\n\`\`\`\n${bodyPreview}\n\`\`\`\n\n`;

// After — matches the existing pattern already used in log_parser_shared.cjs
summary += `**Body Preview:**\n\`\`\`\`\`\`\n${bodyPreview}\n\`\`\`\`\`\`\n\n`;

The 6-backtick convention was already established in log_parser_shared.cjs (line 962: "Use 6 backticks to avoid conflicts with content that may contain 3 or 5 backticks"); these changes bring the remaining callsites in line with it.

Original prompt

---

This section details on the original issue you should resolve

<issue_title>Summary Escaping Broken</issue_title>
<issue_description>The ./actions/setup/md/markdown.md looks like this

<markdown-generation>
<instruction>When generating markdown text, use 4 backticks instead of 3 to avoid creating unbalanced code regions where the text looks broken because the code regions are opening and closing out of sync. Use GitHub Flavored Markdown.</instruction>
<example>
<correct>
````markdown
# Example
```javascript
console.log('hello');
```
````
</correct>
<incorrect>
```markdown
# Example
```javascript
console.log('hello');
```
```
</incorrect>
</example>
</markdown-generation>

I believe that the first triple backtick after the last console.log('hello'); closes the entire block and then that leaves a stray hanging ```

which results in broken summary formatting</issue_description>

Comments on the Issue (you are @copilot in this section)

• Fixes Summary Escaping Broken #17383

---

🔒 GitHub Advanced Security automatically protects Copilot coding agent pull requests. You can protect all pull requests by enabling Advanced Security for your repositories. Learn more about Advanced Security.

[Copilot]

Pull request overview

This PR fixes a markdown rendering bug where content containing triple backticks would break GitHub Actions step summaries by prematurely closing outer code fences.

Changes:

• Updated code fence delimiters from 3 to 6 backticks in summary generation functions
• Added test coverage for content containing triple backticks
• Aligned all callsites with the existing 6-backtick convention established in log_parser_shared.cjs

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated no comments.

File	Description
actions/setup/js/safe_output_summary.cjs	Changed body preview and message details code fences from 3 to 6 backticks
actions/setup/js/log_parser_shared.cjs	Changed safe-outputs body preview code fences from 3 to 6 backticks
actions/setup/js/safe_output_summary.test.cjs	Added tests for body content and error messages containing triple backticks

---

💡 Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.