Introduce a terminal UI with a progress bar and key controls, and add
utilities for collecting and querying boolean Nix options. The toggle
function also allows flipping a boolean value in the source.
The nix module now parses `/* */` comments as categories and associates
them with subsequent options. The output format has been updated to
include the category prefix before the option path. The internal state
is maintained during traversal to ensure correct category propagation
through nested structures.
