ETS-based implementation of ClusterHelper.RoleStore.

Maintains two named ETS tables:

• ClusterHelper.NodeConfig — a :bag table with {:scope, scope, :role, role} → node and {:scope, scope, :node, node} → role entries for bidirectional O(1) lookups
• ClusterHelper.NodeConfig_nodes — a :set table with {:scope, scope, node} entries for O(1) node enumeration per scope

Read operations (get_my_roles/1, get_nodes/2, get_roles/2, all_nodes/1) bypass any GenServer and read directly from ETS with read_concurrency: true.

Table names

Table names are kept as ClusterHelper.NodeConfig and its derived name for backward compatibility with any code that references the ETS table directly.