Set up a local-first Turso database with sync (embedded replicas or push/pull) and understand write behavior

Documented steps

1. Decide the model. Embedded replica (@libsql/client): local file for reads, all writes forwarded to the remote primary. Offline-capable sync (@tursodatabase/sync): local database with explicit push()/pull(), recommended by Turso for new projects needing sync.
2. Embedded replica: `createClient({ url: 'file:local.db', syncUrl: 'libsql://<db>-<org>.turso.io', authToken })`.
3. Sync manually with `await client.sync()`, or pass `syncInterval: 60` (seconds) for periodic background sync.
4. Offline/bidirectional: `npm i @tursodatabase/sync`, then `const db = await connect({ path: './app.db', url, authToken })` and call `await db.push()` / `await db.pull()`; `db.checkpoint()` and `db.stats()` are also available.
5. Call sync() (or pull()) at application start before serving reads, otherwise the first requests read a stale or empty local file.
6. Treat the local file as owned exclusively by the client process — do not open it with another SQLite tool while sync is running.
7. Verify: write through the client, read from a second replica, call sync() on it, and confirm the row appears.