* update the syntax file on_load and on_activated to avoid racey behaviour
* remove setup of custom the pre-defined vars. it's now handled by sh.env(). this fixes the vars not being defined in sh mode
* make sure we chdir before running any command just-in-case something else changed the directory
* pre-defined the variables $_fn, $_nm and $_wd($PWD)
* document the $_nm env var
* clarify the interaction between the pre-defined env vars and the user's shell
* remove RFF to not distract from the syntax def ANN
* ANN the new syntax def