Set builder on indirect's primitive composer for CTE execution

The dependency planner path was setting the builder on pChild's
primitive composer, but not on pb.PrimitiveComposer (the indirect's
composer). When parent's GetBuilder() iterates over indirects to
create the diamond builder, it calls GetBuilder() on each indirect's
primitive composer - which was nil for CTEs.

This fix ensures the builder is also set on the indirect's primitive
composer so the CTE's inner SELECT builder gets included in the
execution graph, allowing the API calls to execute and populate
SQLite tables with data.

Author: claude

internal/stackql/primitivegenerator/select.go

@@ -224,6 +224,11 @@ func (pb *standardPrimitiveGenerator) analyzeSelect(pbi planbuilderinput.PlanBui
 			selCtx := dp.GetSelectCtx()
 			pChild.GetPrimitiveComposer().SetBuilder(bld)
 			pb.PrimitiveComposer.SetSelectPreparedStatementCtx(selCtx)
+			// For indirects (like CTEs), also set the builder on the indirect's primitive
+			// composer so it can be found when parent's GetBuilder() iterates over indirects.
+			if pb.PrimitiveComposer.IsIndirect() {
+				pb.PrimitiveComposer.SetBuilder(bld)
+			}
 			return nil
 		}
 	}