Message, Part (Text/Image/File), ToolCall, FunctionCall, and Usage
now round-trip through JSON. Message uses a type-discriminated
envelope for the Part interface. Required for checkpoint persistence.
Signed-off-by: Aurélien Sibiril <81782+aureliensibiril@users.noreply.github.com>
StreamAccumulator never set its model field, so
Response().Model was always empty for streamed
completions. Add a Model field to stream events
and populate it in all three providers (OpenAI,
Anthropic, Bedrock).
Signed-off-by: Bryan Frimin <bryan@getprobo.com>
