Cohort Grid

Retention by signup week as a real table: a row per cohort, a column per period since signup, and in every cell the number in mono with a dot before it in one data hue's four steps. Younger cohorts have fewer periods and their empty cells draw nothing. An optional row sums up every cohort, weighted by size. The cohort column stays put while the periods scroll sideways inside the grid's own box. Static, with a legend from less to more.