Heliograph evaluation sample

Truncated samples, not complete national datasets. See manifest.json for dates, counts, validation and source hashes. Location rows include source-page URLs.
Changes describe observations between dated snapshots. Appeared/disappeared does not establish a physical opening/closure. A source or parser change can produce events. Coverage warnings require investigation.
No earlier snapshot means no comparable history, not zero real-world changes.
Expected counts are approximate internal references, not independent verification.
