fix: use thread_local last error tracking

Author: anonrig

rust/deps/merve.cpp

@@ -312,8 +312,8 @@ struct StarExportBinding {
   std::string_view id;
 };
 
-// Global state for error tracking
-std::optional<lexer_error> last_error;
+// Thread-local state for error tracking (safe for concurrent parse calls).
+thread_local std::optional<lexer_error> last_error;
 
 // Lexer state class
 class CJSLexer {

src/parser.cpp

@@ -310,8 +310,8 @@ struct StarExportBinding {
   std::string_view id;
 };
 
-// Global state for error tracking
-std::optional<lexer_error> last_error;
+// Thread-local state for error tracking (safe for concurrent parse calls).
+thread_local std::optional<lexer_error> last_error;
 
 // Lexer state class
 class CJSLexer {