Incredibly, I just successfully programmed this beast with that original 78¢ PL2303HX USB/TLL adapter!
[The crowd roars. Closeups of emotional persons weeping and hugging.]
Indeed, the TX and RX terminals must be reversed.
The bootloader used is apparently not the "Mini," but the "Pro or Pro Mini," which may have been part of the problem.
The trick seems to be catching the RESET button let-off at precisely the right moment late in the process. I suspect that there's about a quarter-second window to nail it, but when you get it right, it just pops right in. "Blink" with a reconfigured patterns successfully loaded twice. I don't feel like pressing my luck further.
This has been an educational and edifying experience...I suppose.
Thanks to all...