Add pull request merge support to GitHub Actions

- Add pull_request trigger with closed type
- Add condition to run only when PR is merged or on push to main
- Enable deployment on both direct push and PR merge to main

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <noreply@anthropic.com>

.github/workflows/gh-pages.yml

@@ -4,10 +4,15 @@ on:
   push:
     branches:
     - main
+  pull_request:
+    branches:
+    - main
+    types: [closed]
 
 jobs:
   build-deploy:
     runs-on: ubuntu-latest
+    if: github.event_name == 'push' || (github.event_name == 'pull_request' && github.event.pull_request.merged == true)
     steps:
     - uses: actions/checkout@v4
       with: