chore: import upstream snapshot with attribution

.github/pull_request_template.md

@@ -0,0 +1,27 @@
+## Summary
+
+-
+
+## Type
+
+- [ ] Bug fix
+- [ ] Feature
+- [ ] Documentation
+- [ ] Test or tooling
+- [ ] Maintenance
+
+## Validation
+
+- [ ] `uv run ruff check .`
+- [ ] `uv run ruff format --check .`
+- [ ] `uv run pytest tests/ -x --timeout=60`
+- [ ] Not required; docs-only or metadata-only change.
+
+## Evidence
+
+- Screenshots / recordings / trace files:
+- If runtime, viewer, client, proxy, or UI behavior changed, include `raw.githubusercontent.com` screenshot URLs here.
+
+## Privacy
+
+- [ ] This PR does not include API keys, auth tokens, private prompts, raw trace files, or generated HTML viewers.