step,rule,n_before,n_after,n_removed,rationale
1,first row has no previous row: one-day change undefined,2498,2497,1,changes are between consecutive rows (TASK.md)
2,keep 120 rows before first post_cut=1 row + post_cut=1 rows,2497,0,2497,"no post_cut=1 rows exist, so both estimand windows are empty"