pull_request_template.md

What this changes, and why

Evidence

$ make ...

Invariants

Spec impact

• None. No contract in SPEC.md is touched
• SPEC.md changes are included, and a spec-change issue tracks the decision

Checks

• make gates. If you could not run it, say which suites you ran instead
• make native-smoke, if native/ or driver/src/native/ changed
• No AI attribution trailers in the commits

Anything else