Add ON CLUSTER clause parsing to DELETE statement

Handle DELETE FROM table ON CLUSTER cluster WHERE ... syntax by parsing
the ON CLUSTER clause between the table name and WHERE clause.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

Author: kyleconroy

ast/ast.go

@@ -729,7 +729,8 @@ type DeleteQuery struct {
 	Position  token.Position `json:"-"`
 	Database  string         `json:"database,omitempty"`
 	Table     string         `json:"table"`
-	Partition Expression     `json:"partition,omitempty"` // IN PARTITION clause
+	OnCluster string         `json:"on_cluster,omitempty"` // ON CLUSTER clause
+	Partition Expression     `json:"partition,omitempty"`  // IN PARTITION clause
 	Where     Expression     `json:"where,omitempty"`
 	Settings  []*SettingExpr `json:"settings,omitempty"`
 }

parser/parser.go

@@ -6277,6 +6277,15 @@ func (p *Parser) parseDelete() *ast.DeleteQuery {
 		}
 	}
 
+	// Parse ON CLUSTER clause
+	if p.currentIs(token.ON) {
+		p.nextToken() // skip ON
+		if p.currentIs(token.CLUSTER) {
+			p.nextToken() // skip CLUSTER
+			del.OnCluster = p.parseIdentifierName()
+		}
+	}
+
 	// Parse IN PARTITION clause
 	if p.currentIs(token.IN) {
 		p.nextToken() // skip IN

parser/testdata/02541_lightweight_delete_on_cluster/metadata.json

@@ -1,5 +1 @@
-{
-  "explain_todo": {
-    "stmt8": true
-  }
-}
+{}