Get First Week Holdout

Did the first-week ladder move the habit rate? Treated versus held out.

Reads the durable experiment record the state job writes onto each customer, rather than recomputing the arm from the hash. Recomputing would silently re-label everyone the moment the salt changed, and any drift between the two implementations would read as a real effect.

Only closed windows count. Someone three days past signup cannot yet have four active days, so counting them draws a collapse at the right edge that makes the treated arm look worse the faster it grows.

Expect not_yet for a while. At ~350 signups a day and a 20% holdout, a two point lift needs about forty days and a one point lift is not resolvable at this volume at all. That is a property of the question, not a fault in the answer.