progress

Progress — what a computation is doing right now, as a tree of steps.

• [.step][] — Step, one span of work (a label, a parent, a start time, and optionally a count), and step(), which opens one beneath the ambient step.
• [.registry][] — the process's open steps, and the watchers told when one opens or closes.
• [.flush][] — the watcher that writes open steps to their scratch's index at most ten times a second, so a page in any process can list them.
• [.terminal][] — print_progress, the watcher that draws the tree in a terminal.

A memoized call, a map and a pmap open steps of their own; a recipe body opens one with cg.step. This __init__ is documentation-only; the root imports step and print_progress from the leaves.