Fix script not found error by returning to source branch after push

The workflow was failing with "No such file or directory" when trying to run check_screenshot_changes.sh because:
- update_screenshot_branch.sh switches to the pr-screenshot orphan branch
- After pushing, it didn't return to the original branch
- The next workflow step tries to run check_screenshot_changes.sh
- But that script doesn't exist on pr-screenshot branch (only on PR branch)

Fixed by adding code at the end of update_screenshot_branch.sh to checkout the source branch after pushing. This ensures subsequent workflow steps can access scripts from the PR branch.

Now the workflow will:
1. Generate screenshots on PR branch
2. Switch to pr-screenshot branch and push screenshots
3. Return to PR branch
4. Run check_screenshot_changes.sh (script now available)
5. Comment on PR with changed screenshots

Co-authored-by: richardthe3rd <573334+richardthe3rd@users.noreply.github.com>

Author: Copilot

scripts/update_screenshot_branch.sh

@@ -99,7 +99,6 @@ git add "$PR_FOLDER"/*.png
 
 if git diff --staged --quiet; then
   echo "No screenshot changes to commit"
-  exit 0
 else
   echo "Committing screenshot changes..."
   git commit -m "Update screenshots for PR #$PR_NUMBER [skip ci]"
@@ -109,3 +108,7 @@ else
 
   echo "✓ Screenshots updated successfully to $BRANCH_NAME/$PR_FOLDER"
 fi
+
+# Return to the original branch
+echo "Returning to source branch: $SOURCE_BRANCH..."
+git checkout "$SOURCE_BRANCH"