sessionLock

Single-active-session guard used when docStore is set, to prevent two sessions from concurrently resuming the same persisted document under the same stable actor (which would mint colliding clientSeq values and silently lose edits). Defaults to NoopSessionLock: unlike a browser with multiple tabs, an Android app is one process per store by default, so the hazard this guards against is reachable only when docStore is itself shared across processes. Ignored when docStore is unset. Ported from JS client.ts's sessionLock option; JS's browser-only deactivateOnUnload auto-default has no Android analog (no page-unload event) and is not ported.