The chain as a code outline

// The whole pipeline is a tree view, like the symbols panel in an editor.
// root = generation, the indented branch is the ordered chain, master = output.
// It is keyboard-first: j/k move the cursor, space/enter folds open the focused
// node's editor — which lives right inside the row, never in a detached panel —
// and x/d/del/[ /] act on the selection. / drops the add-effect command palette.