docs: add PR template with dry-run checklist

Closes #9

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: 2 people

.github/pull_request_template.md

@@ -0,0 +1,11 @@
+## What changed and why
+
+## Dry-run result
+
+- [ ] Triggered:
+      `gh workflow run safe-settings-sync.yml --repo IntegratedDynamic/admin --ref $BRANCH -f nop=true`
+- [ ] Output reviewed — no unexpected diffs
+- [ ] Known safe-settings bugs not triggered:
+  - `bypass_pull_request_allowances` not added to any suborg file
+  - `contexts:` uses `[]`, not a placeholder string
+  - No subdirectory added to `.github/suborgs/`