Add PR template section for demo videos (#933)

* Add PR template section for demo videos

* Remove PR template author exemption note

* Refine PR template with review trigger checklist

.github/pull_request_template.md

@@ -0,0 +1,33 @@
+## Summary
+
+- What changed?
+- Why?
+
+## Testing
+
+- How did you test this change?
+- What did you verify manually?
+
+## Demo Video
+
+For UI or behavior changes, include a short demo video (GitHub upload, Loom, or other direct link).
+
+- Video URL or attachment:
+
+## Review Trigger (Copy/Paste as PR comment)
+
+```text
+@codex review
+@coderabbitai review
+@greptile-apps review
+@cubic-dev-ai review
+```
+
+## Checklist
+
+- [ ] I tested the change locally
+- [ ] I added or updated tests for behavior changes
+- [ ] I updated docs/changelog if needed
+- [ ] I requested bot reviews after my latest commit (copy/paste block above or equivalent)
+- [ ] All code review bot comments are resolved
+- [ ] All human review comments are resolved