Salvaged from PR #84199 by @RickyYii. DirectAlias gains api_key/key_env; the direct-alias override re-resolves credentials against the alias endpoint (host-gated, #28660) and reuses the pre-alias key only on an origin match; oneshot -m <alias> passes the alias key as explicit_api_key; direct-alias branch gains the OLLAMA_API_KEY host gate. Fixes #83612.