config.Parse walks the file as written and fails on the first key that
matches no setting, naming its dotted path and line, so a typo in
exclude or prune_grace_period no longer falls back silently. ${...}
references and YAML merge keys still load. config set refuses such a key
before writing. The key-to-field lookup moves from internal/cli to
config.SettingType so both use it.
Model: opus-5-5
