Which override-file layer supplied an env key’s effective value. Ordered
low-to-high by precedence (a later layer shadows an earlier one), matching
the apply order in Config::load_or_init.
Print the effective base preset source, optional overlay, and external
shell deployment mode. This makes built-in, external, and overlay-backed
runs report provenance with the same vocabulary.
Set (Some) or remove (None) one key in a shine.env.toml-shaped override
file, preserving comments/formatting of unrelated entries and the
description of a { value, description } entry being updated. Creates the
file (and its parent directory) if it doesn’t exist yet.