Add BOM handling and enable DropExternalLanguage tests

- Skip UTF-8 BOM at start of input
- Fix JSON field name from Authorization to Owner

86 tests now passing (was 84)

Author: claude

parser/lexer.go

@@ -206,6 +206,10 @@ type Lexer struct {
 
 // NewLexer creates a new Lexer for the given input.
 func NewLexer(input string) *Lexer {
+	// Skip UTF-8 BOM if present
+	if len(input) >= 3 && input[0] == 0xEF && input[1] == 0xBB && input[2] == 0xBF {
+		input = input[3:]
+	}
 	l := &Lexer{input: input}
 	l.readChar()
 	return l

parser/parser.go

@@ -5089,14 +5089,13 @@ func dropCredentialStatementToJSON(s *ast.DropCredentialStatement) jsonNode {
 
 func dropExternalLanguageStatementToJSON(s *ast.DropExternalLanguageStatement) jsonNode {
 	node := jsonNode{
-		"$type":      "DropExternalLanguageStatement",
-		"IsIfExists": s.IsIfExists,
+		"$type": "DropExternalLanguageStatement",
 	}
 	if s.Name != nil {
 		node["Name"] = identifierToJSON(s.Name)
 	}
 	if s.Authorization != nil {
-		node["Authorization"] = identifierToJSON(s.Authorization)
+		node["Owner"] = identifierToJSON(s.Authorization)
 	}
 	return node
 }

parser/testdata/Baselines150_DropExternalLanguage150/metadata.json

@@ -1 +1 @@
-{"skip": true}
+{"skip": false}

parser/testdata/DropExternalLanguage150/metadata.json

@@ -1 +1 @@
-{"skip": true}
+{"skip": false}