It occurred to me that I really needed to at least partially install the ceiling joists in the entryway before connecting the entry walls together. So I cut the small joists...
...tipped the wall back so I could set the joists in place...
...then tipped the wall back up, and screwed together the remaining two walls of the entryway. I added a second top plate to the top of the entryway walls.
I cut out the 2 x 4 across the base of the doorway...
...and attached the ceiling joists in place. (They are spaced in an odd way in anticipation of an exterior ceiling light being installed at some point.)