In case anyone else needs this information…
I managed to get things working. Wired things as in my above post. Loaded up the SpiUartTerminal example sketch from the WiFly-Shield library (which, btw, also needs to have F(x) #defined as no-op). Added one line to the top:
pinMode(10, OUTPUT);
After that, was able to connect to cmd mode, send commands, join a network, and telnet in.
I assumed that the SpiUartTerminal sketch was sufficient in itself (and perhaps it is for the Uno or other boards), but I had to explicitly set the CS pin for OUTPUT to get things working. Always the simple things...