fix(#2872): auto-close PRs that omit the issue-link keyword (#2873)

The Require Issue Link workflow was posting a comment and failing the
status check, but never transitioning the PR to closed. PR templates
promise auto-close behavior; PR #2863 demonstrated the gap (opened
without a Closes #N, sat open until manually closed).

Adds a `pulls.update({state: 'closed'})` call after the existing
comment, updates the comment heading to 'PR auto-closed', and tells
the author how to reopen after fixing the body.

Closes #2872

.github/workflows/require-issue-link.yml

@@ -24,19 +24,20 @@ jobs:
             echo "found=false" >> "$GITHUB_OUTPUT"
           fi
 
-      - name: Comment and fail if no issue link
+      - name: Comment, close, and fail if no issue link
         if: steps.check.outputs.found == 'false'
         uses: actions/github-script@3a2844b7e9c422d3c10d287c895573f7108da1b3 # v9.0.0
         with:
           # Uses GitHub API SDK — no shell string interpolation of untrusted input
           script: |
             const repoUrl = `https://github.com/${context.repo.owner}/${context.repo.repo}`;
+            const prNumber = context.payload.pull_request.number;
             await github.rest.issues.createComment({
               owner: context.repo.owner,
               repo: context.repo.repo,
-              issue_number: context.payload.pull_request.number,
+              issue_number: prNumber,
               body: [
-                '## Missing issue link',
+                '## Missing issue link — PR auto-closed',
                 '',
                 'This PR does not reference an issue. **All PRs must link to an open issue** using a closing keyword in the PR body:',
                 '',
@@ -46,7 +47,13 @@ jobs:
                 '',
                 `If no issue exists for this change, [open one first](${repoUrl}/issues/new/choose), then update this PR body with the reference.`,
                 '',
-                'This PR will remain blocked until a valid `Closes #NNN`, `Fixes #NNN`, or `Resolves #NNN` line is present in the description.',
+                'To resume work after fixing the body: edit the PR description to add a valid `Closes #NNN`, `Fixes #NNN`, or `Resolves #NNN` line, then click **Reopen pull request**. The workflow will re-evaluate on reopen.',
               ].join('\n')
             });
-            core.setFailed('PR body must contain a closing issue reference (e.g. "Closes #123")');
+            await github.rest.pulls.update({
+              owner: context.repo.owner,
+              repo: context.repo.repo,
+              pull_number: prNumber,
+              state: 'closed',
+            });
+            core.setFailed('PR body must contain a closing issue reference (e.g. "Closes #123") — PR closed.');