docs: prepare repository for open-source collaboration

.github/PULL_REQUEST_TEMPLATE.md

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+## Summary
+
+- What changed?
+- Why was this needed?
+
+## Verification
+
+- [ ] `npm ci`
+- [ ] `npm run start` (or relevant platform run)
+- [ ] Relevant manual verification completed
+
+Commands and outputs:
+
+```txt
+<paste commands/results>
+```
+
+## Risk / Impact
+
+- Affected areas:
+- Backward compatibility concerns:
+- Rollback plan (if needed):
+
+## Checklist
+
+- [ ] Scope is focused and minimal
+- [ ] Documentation updated (if behavior/setup changed)
+- [ ] No secrets or credentials added
+- [ ] Screenshots attached for UI changes (if applicable)