A built deck only syncs presenter↔audience on the same machine (BroadcastChannel/localStorage); cross-device needs either the dev server or addSyncMethod + a relay—today served by slidev-addon-sync / slidev-sync-server (related: #1987). Is the philosophy that addSyncMethod is the intended public seam and sync stays in addons, or is there appetite for a batteries-included, relay-based cross-device sync in core? Would a maintained, documented reference sync server be welcome under the org?