docs: Created an authorship policy and PR template that requires explicit acknowledgement of AI assistance

.github/PULL_REQUEST_TEMPLATE/pull_request_template.md

@@ -0,0 +1,11 @@
+### AI assistance (if any):
+- List tools here and files touched by them
+
+### Authorship & Understanding
+
+- [ ] I wrote or heavily modified this code myself
+- [ ] I understand how it works end-to-end
+- [ ] I can maintain this code in the future
+- [ ] No undisclosed AI-generated code was used
+- [ ] If AI assistance was used, it is documented below
+