Use when the user wants to: go "back" after viewing/action, understand why the wrong screen opened, rework menu/buttons (many commands in /help), remove emoji from buttons, add "Cancel" to input mode, or when navigation breaks on reopen (fresh vs history). Covers: states and return context, context flags through layers, inline menu, two-tier navigation, button semantics, emoji discipline, callback delegation, pagination with context, UI tests presence+routing. Do not use for promises/copy (product-promise-contract), format delivery (content-delivery-format), and money (money-path-safety).
