Normalized event emitted by a streaming provider adapter.
Delta payloads are binary fragments. They may end inside a UTF-8 codepoint; the stream session reassembles and validates the bounded trailing bytes before exposing text to a consumer.
@type t() :: %Spectre.Inference.ProviderEvent{ cursor: term(), kind: term(), metadata: term(), payload: term(), provider_request_id: term(), provider_sequence: term(), usage: term(), usage_quality: term() }
@spec completed( Spectre.Inference.Response.t() | String.t() | map(), keyword() ) :: t()
@spec delta( binary(), keyword() ) :: t()
@spec new( atom(), keyword() ) :: t()