Returns per-week brand sentiment (positive/neutral/negative percentages)
+sourced from the Semrush Sentiment element (not Adobe Postgres), rolled up
+from daily rows into ISO weeks. Emits the legacy sentiment-overview
+contract verbatim so the existing chart consumes it drop-in — absolute
+values differ from the Postgres-backed legacy endpoint, but the shape and
+sentiment[] ordering/colors are identical.
+
Brand-scoped via the brand's Semrush sub-workspace (resolved from :brandId);
+region (when not all) is resolved to a Semrush project_id server-side,
+category becomes a category__<label> tag, and model/platform are
+translated to a Semrush model server-side.
+