How to make a new SSD bootable?
It seems to work now after one more tweak; I posted the question because I hope it's of use to some other lost soul.

I tried erasing the SSD once more with Disk Utility. This time I did two things differently: 1) I used the default name 'Untitled' for the disk, and 2) I used the default 'Mac OS Extended' option for the file system instead of APFS when erasing the disk. This time the OS install proceeded successfully past the first reboot.

Thing #2 is probably what matters, but it's unclear why. It is also possible that some of the dinking around with bless had something to do with the success this time, but I doubt it.