Mostly for consistency with the other two binaries.
'sfdoc' is easier to type and resembles 'pydoc' and 'perldoc' so it's even easier to remember.
Turns out that since shellfu-doc uses pretty.sh (and makes good use of it), what we had was broken cyclic dependency. shellfu-doc and shellfu-embed are useful mostly for developers, though, so it's no shame to split them.