Codex auth failure fixed; API key now uses standard Bearer header

Patch Changes

• b89a04e: ctx7 setup now writes the API key as a standard Authorization: Bearer <key> header instead of a custom CONTEXT7_API_KEY header. Codex resolves a server's auth mode from bearer_token_env_var or a header literally named Authorization, so a custom name read as "no credential configured": Codex fell through to an OAuth credential stored against the same server name and URL, refreshed it during startup, and when that refresh token was dead the server failed with invalid_grant before the API key was ever sent. The hosted endpoint accepts both header forms, so existing configs keep working.