feat(dml): implement DML statement formatting and tests

* Add formatDML function for formatting top-level DML statements
* Introduce tests for various DML scenarios including SELECT, INSERT, UPDATE, and DELETE
* Enhance printer to handle DML statements correctly

pkg/format/format.go

@@ -52,6 +52,12 @@ func (p *printer) writeItem(n cst.Node) {
 	switch v := n.(type) {
 	case *cst.CreateFunction:
 		p.writeCreateFunction(v)
+	case *cst.Raw:
+		if isDMLStart(v.Toks) {
+			p.b.WriteString(formatDML(v.Toks, p.st))
+		} else {
+			p.b.WriteString(verbatimSpan(v.Toks))
+		}
 	default:
 		p.b.WriteString(verbatimSpan(cst.Tokens(n)))
 	}
@@ -160,6 +166,13 @@ func (p *printer) trailingComments(lead cst.Trivia) {
 // tightOps are operators printed without surrounding spaces.
 var tightOps = map[string]bool{"::": true, ":": true, "->": true, "->>": true}
 
+// parenKws are keywords that always take a space before '(' because they
+// introduce a subquery or a bracketed clause, not a function-call argument list.
+var parenKws = map[string]bool{
+	"as": true, "exists": true, "in": true, "not": true,
+	"between": true, "like": true, "ilike": true, "similar": true,
+}
+
 func needSpace(a, b lexer.Token) bool {
 	// No space after.
 	switch a.Kind {
@@ -177,6 +190,11 @@ func needSpace(a, b lexer.Token) bool {
 	case lexer.LParen:
 		switch a.Kind {
 		case lexer.Ident, lexer.QuotedIdent, lexer.RParen, lexer.RBracket, lexer.Param:
+			// Keywords like AS/EXISTS/IN introduce subqueries or clause groups,
+			// not function calls — always separate with a space.
+			if a.Kind == lexer.Ident && parenKws[lowerASCII(a.Text)] {
+				return true
+			}
 			return false // function call / type modifier
 		}
 	case lexer.LBracket: