Does the landlord either have to include in the lease or otherwise disclose to leasee his
Intent to show said property for sale, while said leasee occupies the home?

I can depend on location, but in most there is general clause to allow landlord to enter property with notice, be it 48 hour or 24 hour notice. So normally they may just do so, using existing enter rules even if not spelled out just for sale. But if one is being written it is good to include it.