chore: add pull request template

.github/pull_request_template.md

@@ -1,13 +1,32 @@
 ## Summary
 
-## Safety impact
+Briefly describe what this pull request changes.
 
-- [ ] Changes query classification
-- [ ] Changes protocol handling
-- [ ] Changes fail-open/fail-closed behavior
-- [ ] Adds or updates tests
-- [ ] Updates documentation/changelog
+## Why
 
-## Verification
+Explain the problem being solved or the reason for the change.
 
-Describe the tests performed and the database/client versions used.
+## Validation
+
+- [ ] Focused tests passed
+- [ ] Full test suite passed
+- [ ] `python -m compileall -q sql_safety_proxy` passed
+- [ ] `python -m pip check` passed
+- [ ] `git diff --check` passed
+- [ ] Real database validation completed when relevant
+- [ ] Docker validation completed when relevant
+
+## Compatibility
+
+Note any impact on:
+
+- `ohmydb` CLI
+- legacy `sql-safety-proxy` CLI
+- `sql_safety_proxy` Python package
+- PostgreSQL
+- MySQL/MariaDB
+- configuration or deployment
+
+## Notes
+
+Add any implementation details, limitations, screenshots, or follow-up work.