G-Counter CRDT for offline sync

Implement a G-Counter (Grow-only Counter) CRDT for an offline-first Expo/React Native app.

A G-Counter is a Conflict-free Replicated Data Type where each replica (e.g. a device with an Expo SecureStore-assigned replicaId) tracks its own increments in a private slot. Counters are persisted locally (AsyncStorage / expo-sqlite) and merged whenever the device reconnects — taking element-wise max guarantees the replicas converge without a server or consensus. The total value is the sum of all slots.

Write four functions:

1. createGCounter(replicaCount) — return an array of replicaCount zeros
2. increment(counter, replicaId) — return a new counter with slot replicaId incremented by 1
3. merge(counterA, counterB) — return a new counter where each slot is Math.max of the two
4. value(counter) — return the sum of all slots