OPENAI_ONLY_AGENT_OVERRIDES was rewriting explore and librarian back to
gpt-5.4 medium for OpenAI-only installs. Match the runtime primary so the
install default stays on gpt-5.4-mini-fast.
Keep install-time and runtime model tables in sync, stop OpenAI-only misrouting when OpenCode Go is present, and add valid OpenAI fallbacks for atlas, metis, and sisyphus-junior.
Ultraworked with [Sisyphus](https://github.com/code-yeongyu/oh-my-openagent)
Co-authored-by: Sisyphus <clio-agent@sisyphuslabs.ai>