A Settings paired with its per-leaf SettingsProv. Bundled because every
non-init CliResult variant needs both, the active values for runtime use
and the provenance for source attribution (/settings API and
config show). prov is Arc so it can move into the app state without a
re-allocation; SettingsProv is also large enough that an inline owned
value would balloon CliResult.
Settings of the running kellnr start, resolved from the same command
line, environment and config file as at startup. For code that runs before
the settings are passed around, like the database migrations. None if the
process was not started with valid kellnr arguments, for example in tests.