Workhorse should work for DWS without commenting out code

In !197267 (merged), we documented how to change some code in workhorse and restart workhorse to make it compatible with Agentic Chat in the Web UI, which uses Duo Workflow Service on the backend. Perhaps with an environment variable. Using environment variables in the code isn't ideal because customers may try to set them in production as a workaround. Maybe an env check instead?

Instead of requiring this workaround, we should have code that works in dev mode.

In addition, we should document in doc/development/duo_agent_platform/_index.md that if someone sees the error "Error: Unable to connect to workflow service. Please try again." in agentic Chat, workhorse is the likely root cause.