fix: escape backticks and special chars in commit message for GitHub Action (#1928)

The `issue-closed-comment` workflow fails when commit messages contain
backticks because they're interpolated directly into JS template
strings, breaking syntax.

### Changes
- Escape backslashes, backticks, and `${` sequences before setting the
commit message output
- Order matters: backslashes first to avoid interfering with subsequent
escaping

```javascript
// Before: raw message breaks template string if it contains backticks
core.setOutput('commit_message', commit.message);

// After: properly escaped for safe interpolation
const escapedMessage = commit.message.replace(/\\/g, '\\\\').replace(/`/g, '\\`').replace(/\$\{/g, '\\${');
core.setOutput('commit_message', escapedMessage);
```

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<details>

<summary>Original prompt</summary>

> the github action which comments on issue closure fails when the
commit message contains ` since these are js strings. Make sure to
escape them.


</details>



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.github/workflows/issue-closed-comment.yml

@@ -53,7 +53,9 @@ jobs:
               
               core.setOutput('closed_by_commit', 'true');
               core.setOutput('commit_sha', commitId);
-              core.setOutput('commit_message', commit.message);
+              // Escape backslashes, backticks and ${ to prevent breaking JS template strings
+              const escapedMessage = commit.message.replace(/\\/g, '\\\\').replace(/`/g, '\\`').replace(/\$\{/g, '\\${');
+              core.setOutput('commit_message', escapedMessage);
               core.setOutput('commit_url', closedEvent.commit_url);
             } else {
               console.log(`ℹ️  Issue #${issueNumber} was closed manually (not by commit)`);