What a running process appears to be doing, inferred from its terminal
signals. Orthogonal to ProcessState: the lifecycle
says whether a child is alive, this says whether it is busy or waiting on the
user. The TUI maps it to a sidebar accent; the domain stays free of rendering.
Lifecycle state of a managed process. The TUI adapter maps this to a sidebar
status glyph and color; the domain itself stays free of rendering concerns.