County planning staff are set to pitch an amendment clarifying county development code language that caps accessory-unit rooms at three per house and prohibits short-term rentals of those rooms, following up on a trio of workshops on affordable housing held last fall by the Board of Supervisors. “We want to make it very clear that the expectation is…you cannot make that room available for short-term rentals,” said Tom Lai, the assistant director of the county’s…