Get Overview Send Activity

Pooled send-relative activity curve across active MDP-state experiments: per integer hour-delta in [-12, +12] from each member's send anchor, how many treatment (enqueued) and held-back control members were active (fired >=1 event in that hour bucket). The treatment − control gap at positive deltas is the send's activation lift; the negative-delta region is the randomization balance check. Sends are windowed to the last window_days ending one day ago so every member's +12h tail is observable. Rate-limited per (org, user); the Overview drives it on mount and on window change.