NodeLike:     |BaseNode     |BaseAgent     |BaseTool     | ((...args:never[])=>unknown)     |"START"
Any value that can be converted to a workflow node: a node, a tool, a plain
function, or the 'START' sentinel literal. (Agent wrapping is added in
Phase 3 via build_node.)
Any value that can be converted to a workflow node: a node, a tool, a plain function, or the
'START'sentinel literal. (Agent wrapping is added in Phase 3 viabuild_node.)