Public data ingestion pipeline

1. Resolve the Ontario Data Catalogue resource metadata and license.
2. Download the versioned ZIP to a disposable staging directory.
3. Verify the expected file list and record the ZIP SHA-256.
4. Copy only the documented fixture subset into 20_sources/open-data/.
5. Run the no-data scan, contracts, and source-quality checks.

The committed snapshot is refreshed only through Refresh public sources runbook.