Add pull request description template

Author: Eliezir

.github/pull_request_template.md

@@ -0,0 +1,25 @@
+<!-- Closes #<issue> (delete if not applicable) -->
+
+## Summary
+
+<What changed and why, in 1–3 sentences. Lead with the user-visible behavior before/after; leave implementation for the next section.>
+
+## How
+
+<Bullet the key changes by file or concern. Call out anything non-obvious: reused logic from another branch, deviations from existing patterns, latent bugs noticed but not fixed here.>
+
+## Scope
+<!-- Optional — delete if there's nothing worth flagging. -->
+
+<What this PR does *not* touch. Explicitly name adjacent systems (prod builds, electron, Docker, etc.) that a reviewer might assume are affected.>
+
+## Questions
+<!-- Optional — delete if none. -->
+
+<Open decisions, tradeoffs the reviewer should weigh in on, or things you're uncertain about.>
+
+## Test plan
+
+- [ ] <Concrete steps a reviewer can run>
+- [ ] `pnpm typecheck` passes
+- [ ] `pnpm test` passes