chore: add AI assistance disclosure to PR template and CONTRIBUTING (#3398)

.github/pull_request_template.md

@@ -59,3 +59,17 @@ Fixes #
        Frontend:  cd frontend && pnpm format && pnpm lint && pnpm typecheck && BETTER_AUTH_SECRET=local-dev-secret pnpm build && make test
        Frontend E2E (if you touched frontend/): cd frontend && make test-e2e -->
 
+
+## AI assistance
+
+<!-- DeerFlow is an AI project — most PRs here use AI coding tools, and that's
+     welcome. Disclosing it just helps reviewers calibrate how closely to read the
+     diff. Please fill all three; don't delete the section. -->
+
+**Tool(s) used:** <!-- e.g. Claude Code, Cursor, GitHub Copilot, Codex, Windsurf, or "none" -->
+
+**How you used it:** <!-- e.g. "generated the module from a spec", "autocomplete only",
+     "AI wrote tests, I wrote the impl". A prompt or conversation link is great too. -->
+
+- [ ] I've read and understand every line of this change and take responsibility for it — it's not unreviewed AI output.
+

CONTRIBUTING.md

@@ -287,6 +287,21 @@ Nginx (port 2026) ← Unified entry point
    git push origin feature/your-feature-name
    ```
 
+## AI assistance disclosure
+
+DeerFlow is an AI project and we welcome AI-assisted contributions. To help
+reviewers calibrate how closely to read a change, **every pull request must
+complete the "AI assistance" section of the
+[PR template](.github/pull_request_template.md)**:
+
+- which tool(s) you used (or `none`),
+- how you used them, and
+- a confirmation that a human has read, understands, and takes responsibility
+  for the change.
+
+Please don't delete the section. PRs that ignore it may be asked to fill it in
+before review.
+
 ## Testing
 
 ```bash