- WorkflowRunResponse.mode: Literal["workflow"] (was str) — only one
valid value, so Literal makes the contract explicit.
- WorkflowRunData.outputs: Field(default_factory=dict) — matches the
sibling metadata field's idiom; avoids the mutable-literal-default
smell flagged in code review.
- Extends test_response_models_dump_per_mode with an explicit assertion
on the WorkflowRunResponse.mode echo + exercises CompletionMessageResponse
(was imported-but-unused).