Whether the fork's rules are currently active on the node.
Computed by the canonical isForkActive gate node-side; the SDK
uses this directly without recomputing.
Configured activation height for the fork. null means the fork
is configured but unscheduled (the SDK should treat this as
"fork will not activate during this RPC's lifetime").
In-memory cache of the latest block height the node has
processed. Lets clients do their own near-fork detection without
an extra getLastBlockNumber call.
Per-fork status entry.