chore: import upstream snapshot with attribution

.github/PULL_REQUEST_TEMPLATE/pull_request_template.md

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+### Summary
+
+<!-- Please give a short summary of the change and the problem this solves. -->
+
+### Test plan
+
+<!-- Please explain how this was tested -->
+<!-- If verification could not complete because of local environment setup, include the failing command, the missing dependency, and why it is unrelated to this PR. Leave the pass checkbox below unchecked until all verification steps pass. -->
+
+### Issue number
+
+<!-- For example: "Closes #1234" -->
+
+### Checks
+
+- [ ] I've added new tests, if relevant
+- [ ] I've run `.agents/skills/code-change-verification/scripts/run.sh`
+- [ ] I've confirmed all verification steps pass
+- [ ] If using Codex, I've run `/review` before submitting this PR