The sleeves are on!
After I sewed them on, I finished that seam with bias tape. It was kind of fiddly work. There were places along the seam where the fabric was several layers thick (at the back yoke seams) where I had to pin the bias to the inside and then pin it around the outside too. With pins on the upper and lower sides of the seam as it is feeding through the sewing machine, you have to go slowly and carefully so as not to jam your needle on all those pins, or catch the pins under the plate where the feed dogs are. (That unfinished looking seam on the above photo is the zigzagged one inside the sleeve.)
It doesn't look too beautiful but it is on the inside of the jacket and won't be seen except as a flash when I take the jacket off.
Somebody asked in a previous comment if I'd lengthened the jacket (no) and if the back was longer than the front (also no). This photo sort of shows that the jacket is the same length all around. (The blue top on Pinky isn't on straight.) And the jacket is pretty short - it will just stop at my waist when hemmed - but that's the style so I didn't change the length.
Here's the front with sleeves. I have turned one up just to see what it might look like because of the V detail on the bottom of the 3/4 sleeve.
Here it is from the back, with one sleeve turned up. The pattern doesn't call for any turning up of the sleeves but I didn't shorten them when I made them and they are a tad longish. Next time I make this, I will shorten the sleeve pattern piece by about 3/4 of an inch. My arms are not weirdly short and they don't look funny but I usually have to take up regular length sleeves and I wondered what would happen with the 3/4 sleeve if I didn't take it up, since it was short to begin with. It's all about proportion.