When 'hermes model' runs against a providers: (keyed-schema) entry that
relies only on key_env, the picker resolves the env var for the live
/models request and then wrote a synthesized 'api_key: ${KEY_ENV}' back
to the providers.<key> entry. That's redundant — the runtime already
resolves from key_env directly — and it clutters configs that
intentionally keep credentials out of config.yaml.
Only persist provider_entry['api_key'] when the user originally had an
inline value (literal secret or ${VAR} template). Entries that declared
only key_env stay clean on save.
Fixes#15803.
8258f4dcb7