Pure formatting pass from `cargo fmt --all`. No logic changes. Separating
this out so the 1.9 release feature commits that follow show only their
intentional edits.
YamlWorkflowFile supports both single (workflow:) and multi (workflows:)
formats. WorkflowSpec gains typed inputs/outputs declarations.
Type string parser for inline types ("string?", "list<number>", etc.).
load_workflow_from_str returns Vec<CompiledWorkflow>.
Backward-compatible load_single_workflow_from_str convenience function.