fix: improve maintenance and synchronize live conversations

CONTRIBUTING.md

@@ -70,6 +70,19 @@ chmod +x .git/hooks/prepare-commit-msg
 4. Commit with sign-off (`git commit -s`).
 5. Push and open a Pull Request, filling out the PR template.
 
+### Python unused-code check
+
+Ensure Ruff 0.17.3 is on `PATH` (for example, install it with
+`uv tool install ruff==0.17.3`). From the repository root, run:
+
+```bash
+./scripts/check-python-unused.sh
+```
+
+The script checks `backend/`, `deploy/`, `e2e/`, and `relicense_headers.py`.
+F401 catches unused imports; F841 catches assigned local variables that are
+never used. Ruff is developer tooling, not a business/runtime dependency.
+
 ## License headers
 
 New source files should carry the standard Apache-2.0 header. You can apply or