Environment

Variable	Purpose	Default
`DOMA_HOME`	doma's config + state directory.	`~/.config/doma`
`DOMA_DB`	Path to the SQLite database.	`<DOMA_HOME>/doma.db`
`DOMA_CONFIG`	Path to `config.yml`.	`<DOMA_HOME>/config.yml`
`NO_COLOR`	If set (any value), disables ANSI colors. Honored by default; `--color` overrides.	unset
`COLUMNS`	Terminal width hint. Used by the picker for layout.	autodetected
`SHELL`	Read by `setup install` to pick the right rc file.	from process env

Each path-shaped variable is ~-expanded before use. Pre-existing tilde is fine:

DOMA_HOME=~/scratch-doma doma list   # works as expected

Misconfiguration → friendly errors

Pointing an env var at the wrong kind of thing surfaces as a clean ConfigError, not an internal trace:

$ DOMA_HOME=/etc/passwd doma list
✗ DOMA_HOME points at a file, not a directory: /etc/passwd

$ DOMA_DB=/var doma list
✗ DOMA_DB points at a directory, not a file: /var

Both exit 5 (the ConfigError exit code) so scripts can branch on it.