FSM state for Eval (M-:) mode.
Carries the eval input string typed so far, plus the standard count/leader fields.
Summary
Types
@type t() :: %Minga.Mode.EvalState{ count: non_neg_integer() | nil, input: String.t(), leader_keys: [String.t()], leader_node: Minga.Keymap.Bindings.node_t() | nil }