docs: add clarifying comment for count measure key mapping

Agent-Logs-Url: https://github.com/objectstack-ai/objectui/sessions/7e803790-d91b-4542-886e-743490f0dfc6

Co-authored-by: hotlong <50353452+hotlong@users.noreply.github.com>

Author: Copilot

packages/data-objectstack/src/index.ts

@@ -855,6 +855,8 @@ export class ObjectStackAdapter<T = unknown> implements DataSource<T> {
 
       // Map measure keys back to the original field name so that consumers
       // (ObjectChart, DashboardRenderer, etc.) can access values by field name.
+      // This includes count → field (e.g. 'count' → 'amount') to match the
+      // output format of aggregateClientSide() which always uses params.field.
       return rawRows.map((row: any) => {
         const mapped = { ...row };
         if (measureName !== params.field && measureName in mapped) {