test(v2-ingestion): harden public-source schema contract and docs

CONTRIBUTING.md

@@ -63,6 +63,15 @@ git checkout -b feature/your-feature-name
 3. Implement with focused commits and tests.
 4. Open PR: `feature/*` -> `develop`.
 
+## Running Tests (v2)
+
+Runtime images are intentionally lean and may not ship `pytest`.
+Use the development compose stack and install dev dependencies before running tests:
+
+```bash
+docker compose -f docker-compose.yml -f docker-compose.dev.yml run --rm web sh -lc "export PYTHONUSERBASE=/tmp/pyuser && python -m pip install --user -r requirements/dev.txt && python -m pytest -q"
+```
+
 ## PR Checklist
 
 - [ ] Target branch is correct