Upgrade to 1.0.0-rc875

Concerns: pushword/flat

A no-op pw:flat:sync leaves pages untouched

Re-importing a file whose dates the database already holds no longer marks the page as updated, so an unchanged sync stops bumping updatedAt on every page of the host and rewriting every .md with a new revision: stamp. Nothing to do — but note that displayed “updated on” dates and JSON-LD dateModified stop announcing the last sync’s date; past real edit dates, where overwritten, remain in your content files’ git history.