fix: Prevent duplicate issue creation in PR automation workflow

The workflow was creating duplicate issues when multiple trigger events
(opened, edited, synchronize, etc.) fired in quick succession. Both
workflow runs would check the PR simultaneously, find no issue reference,
and each create a new issue.

Added a check to search for existing issues created by this automation
before creating a new one. The workflow now searches for open issues that
contain the PR URL and were created by github-actions bot, preventing
duplicate issue creation.

Fixes the issue where PR #6386 had two issues created (#6499 and #6500).

Author: cursoragent

.github/workflows/create-issue-for-unreferenced-pr.yml

@@ -68,6 +68,18 @@ jobs:
               return;
             }
 
+            // Check if there's already an issue created by this automation for this PR
+            // Search for issues that mention this PR and were created by github-actions bot
+            const existingIssuesResponse = await github.rest.search.issuesAndPullRequests({
+              q: `repo:${context.repo.owner}/${context.repo.repo} is:issue is:open "${prUrl}" author:app/github-actions in:body`,
+            });
+
+            if (existingIssuesResponse.data.total_count > 0) {
+              const existingIssue = existingIssuesResponse.data.items[0];
+              console.log(`An issue (#${existingIssue.number}) already exists for PR #${prNumber}, skipping creation.`);
+              return;
+            }
+
             core.warning(`PR #${prNumber} does not have an issue reference. Creating a new issue so it can be tracked in Linear.`);
 
             // Construct the title and body for the new issue