[CI] Chore: Improve Linear Issue Check Syntax (#5508)

CNCT-2462
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## PR-Codex overview
This PR introduces a new GitHub Actions workflow named `Linked Issue`, which checks for valid issue references in the pull request body. It ensures that the body contains an issue ID with specified prefixes before allowing the pull request to proceed.

### Detailed summary
- Added a new workflow file named `issue.yml`.
- Set the workflow to trigger on `pull_request` events (opened, edited).
- Defined an environment variable `VALID_ISSUE_PREFIXES` with values "CNCT|DASH".
- Created a job named `linear` that runs on `ubuntu-latest`.
- Implemented a step to check for linked issue references in the PR body using a regex.
- If no valid reference is found, the workflow fails with a specific error message.

> ✨ Ask PR-Codex anything about this PR by commenting with `/codex {your question}`

<!-- end pr-codex -->

.github/workflows/issue.yml

@@ -0,0 +1,36 @@
+name: Linked Issue
+
+on:
+  pull_request:
+    types: [opened, edited]
+
+env:
+  VALID_ISSUE_PREFIXES: "CNCT|DASH"
+
+jobs:
+  linear:
+    name: Linear
+    runs-on: ubuntu-latest
+    steps:
+      - name: Check for linked issue
+        uses: actions/github-script@v7
+        with:
+          script: |
+            const pr = await github.rest.pulls.get({
+              owner: context.repo.owner,
+              repo: context.repo.repo,
+              pull_number: context.issue.number
+            });
+            
+            const body = pr.data.body || '';
+            const issueRegex = new RegExp(`(${process.env.VALID_ISSUE_PREFIXES})-\\d+`, 'i');
+            
+            if (!issueRegex.test(body)) {
+              core.setFailed(
+                `No valid issue reference found. PR body must contain an issue ID with one of these prefixes: ${process.env.VALID_ISSUE_PREFIXES}`
+              );
+              return;
+            }
+            
+            const matches = body.match(issueRegex);
+            console.log(`Found issue reference: ${matches[0]}`);