Returns a daily merged-PR series (both github and gitlab sources combined) for the organization, one call for the whole [startDate, endDate] range. Without groupBy, returns the plain workspace daily total (one row per UTC calendar day). With groupBy=orgUnit, returns one row per (day, department) instead, using the point-in-time department the merging user belonged to on that day (SubscriberDirectoryLink -> OrgUnitMembership, valid_from inclusive / valid_to exclusive, primary membership only) -- a mid-range department transfer splits correctly by day. Users who never resolve to a department are bucketed under orgUnitId=null, orgUnitName="Unassigned" rather than dropped, so grouped totals still reconcile against the ungrouped total. orgUnitId scopes the result to that department's subtree (includeDescendants=true) or that department alone (false, the default); the Unassigned bucket is excluded whenever orgUnitId is set, since an unresolved user cannot be "under" a specific department. Capped at 35 days per request, matching granularity=day above. There is no commits field: this reconciles by construction against getVcsPrsSummary's merged-PR totals, which is the only per-day PR source with department attribution today.