> (bash won't let me automatically run a command before and after each interactive command I execute, which I want for task completion notifications

Not to put you off investigating alternative shells (I've spent time with rc shell, xonsh (and tako), and even turned gauche scheme & tcl into a commandline shell), but isn't your bash problem solved by using $PS1 to launch your own functions to do whatever?

At least, you can use $PS1 for the "after command" bit. For pre-command, just use a simple 1 letter wrapped script which does whatever, and then exec's the remaining arguments (aka "Bernstein chaining")

(unless I've gotten the wrong end of the stick, and am missing what you meant)