Refine release notes extraction to include content between gitstream placeholders and update output format

Author: MishaKav

.github/workflows/create-tag-on-merge.yml

@@ -41,14 +41,14 @@ jobs:
               const pull_number = prs[0].number;
               const { data: pr } = await github.rest.pulls.get({ owner, repo, pull_number });
               
-              // Extract only the Purpose section from PR description
+              // Extract content between gitstream placeholders, excluding header and footer
               let releaseNote = pr.title;
 
               if (pr.body) {
-                const purposeMatch = pr.body.match(/Purpose:\s*([^\n]+)/);
+                const contentMatch = pr.body.match(/<!--start_gitstream_placeholder-->.*?### ✨ PR Description\s*(.*?)\s*_Generated by LinearB AI.*?<!--end_gitstream_placeholder-->/s);
 
-                if (purposeMatch) {
-                  releaseNote = purposeMatch[1].trim();
+                if (contentMatch) {
+                  releaseNote = contentMatch[1].trim();
                 }
               }
               
@@ -71,11 +71,10 @@ jobs:
 
           # Create release notes with PR title, description, and link
           cat > release_notes.md << EOF
-          ## ${PR_TITLE}
+          ## What's Changed
 
+          - ${PR_TITLE} in [#${PR_NUMBER}](https://github.com/${{ github.repository }}/pull/${PR_NUMBER})
           ${RELEASE_NOTES}
-
-          **Pull Request:** [#${PR_NUMBER}](https://github.com/${{ github.repository }}/pull/${PR_NUMBER})
           EOF
 
           cat release_notes.md