Resolve the [interpreter] options into Settings constructor kwargs.
Only the interpreter group is resolved through the manifest. Credentials,
the shell allow-list, and the LangSmith project keep their dedicated
loaders in config.py (their empty-string-to-None and reload semantics
do not fit the generic resolver), so this stays scoped to the section whose
defaults this module owns.
Parsed config.toml; loaded automatically when omitted.
