fix: mark window functions as aggregate expressions for CTE compatibility

Window functions (those with OVER clause) are computed expressions that
should not be looked up in underlying tables or CTEs. By setting
IsAggregateExpr = true for window functions, we allow them to bypass
column resolution in indirect queries (CTEs, subqueries, views).

This fixes "cannot find col" errors when using window functions like
RANK(), ROW_NUMBER(), SUM() OVER, etc. in queries that reference CTEs.

Author: claude

internal/stackql/parserutil/parser_util.go

@@ -638,6 +638,11 @@ func inferColNameFromExpr(
 			retVal.IsAggregateExpr = true
 			retVal.Type = aggCol.getReturnType()
 		}
+		// Window functions (with OVER clause) are computed expressions
+		// that don't need to be resolved from underlying tables/CTEs
+		if expr.Over != nil {
+			retVal.IsAggregateExpr = true
+		}
 		if len(funcNameLowered) >= 4 && funcNameLowered[0:4] == "json" {
 			decoratedColumn := strings.ReplaceAll(retVal.Name, `\"`, `"`)
 			retVal.DecoratedColumn = getDecoratedColRendition(decoratedColumn, alias)