Fold the list/mapping parser INSIDE the existing string-typed-value coercion guard (the `not isinstance(_default_value_for_key(key), str)` block from e4ea0a0ed) instead of running it unconditionally, so a genuinely string-typed setting whose value merely starts with '[' or '{' is left untouched while non-string keys get JSON/YAML flow literals parsed to real lists/dicts.
Update website/docs/user-guide/configuring-models.md: the `config set only writes scalar values` note is no longer accurate; document the list/mapping support with a quoted example.
Fixes#40545#50168
Sam Liu
6f2a4676a9