Persistence

Three tiers: the in-memory model, local storage (a record store holding every object pool's rows, plus a content-addressable blob pool), and the cloud, which holds the same rows one record per row, with a version per pool. Each document is its own pool; a folder's contents are the documents whose root rows are placed under it. Mutations are stored locally at the end of each event loop and committed to the cloud asynchronously, as the records changed since the pool's last acknowledged version.