Re-exports of the v2 wire types per ADR 0015. v2 is shipped as
part of inferd-client 0.2 so consumers building against v2 can
reach the proto types without a separate inferd-proto dep.
Conversation role on a v2 message.
Same set as v1’s Role (system / user / assistant) but defined
independently so v1 and v2 can evolve their role enums without
affecting each other. Tool roles are not a separate
conversation-role variant in v2: a tool invocation is an
assistant-role message containing a tool_use content block,
and the result is a user-role message containing a
tool_result content block. This matches Anthropic’s shape.