Manual testing against the live API showed the Keenable REST endpoint
(/v1/search) returns 401 without a key — the keyless "free tier" applies
only to the CLI, not the HTTP API. Treat Keenable like every other
key-based provider: fall back to DuckDuckGo when no key is configured,
and drop the now-inaccurate free-tier wording from the docs.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>