Ok, I figured it out. This was the clue I needed.
The apboot commands need to be on one line (the wiki shows them on multiple):
setenv apb_rb_openwrt "setenv ipaddr 192.168.1.236; setenv serverip 192.168.1.170; netget 0x84000000 ap105.bin; go 0x84000040"
setenv apb_fb_openwrt "cp.b 0xbf040000 0x84000000 0x10000; go 0x84000040"
setenv bootcmd "run apb_fb_openwrt"
saveenv
The commands have newlines on the wiki. They show no matter how wide your browser window is. Might be worth updating to save the next apboot noob some frustration.
Really appreciate all of the of hand-holding @evs !