Adds a site.history command (WHP mode, only when history_list answers) opening a modal of saves/publishes by day. Preview opens the snapshot re-exported with its own design; Restore site / Restore one page load the snapshot as unsaved state (history cleared, dirty marked) so the user still clicks Save. Refs #51 Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>