Discovery! \qedhere
Just made an exciting discovery! The TeX command \qedhere can be used within an AMS proof environment; it forces the proof-tombstone to go on the present line, whereas it would normally go after the end of the \begin{proof}/\end{proof} block, which often puts it outside an itemize or enumerate environment, looking ugly on a line of its own. Of course, the command properly suppresses the tombstone at the end of the proof environment. Ah comfort, O infinite luxury of macros!