The is_existing check included 'get_config_path().exists()' which is
always True after installation (the installer copies config.yaml from
the template). This caused the wizard to enter quick mode, which
skips provider selection entirely — leaving hermes non-functional.
Fix: only consider it an existing installation when an actual
inference provider is configured (OPENROUTER_API_KEY, OPENAI_BASE_URL,
or an active OAuth provider). Fresh installs now correctly show the
full setup flow with provider selection.