\setuplayout[grid=yes] \showgrid

\definegridsnapping[chapter][mindepth,maxheight,local]

\setupwhitespace[none]
\setupblank[line]

\setuphead[chapter][grid=chapter,after=\blank] % ,alternative=top]

\starttext
    \chapter{one}        \input tufte
    \chapter{one\\two}        \input tufte
    \chapter{one\\two\\three} \input tufte
\stoptext
