chore: add PR template for consistent PR descriptions (#31)

Closes #30

Co-authored-by: gss <tbag9199@gmail.com>
Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: 3 people

.github/pull_request_template.md

@@ -0,0 +1,18 @@
+## Related Issue
+
+<!-- Required: Link the issue this PR addresses. CI will fail if no issue is linked. -->
+
+Closes #
+
+## Summary
+
+<!-- Brief description of changes (1-3 bullet points) -->
+
+-
+
+## Test Plan
+
+<!-- How was this tested? -->
+
+- [ ] Unit tests pass
+- [ ] Lint passes