fix: use strict comparison (===) instead of weak comparison (==) in Serializer.php

- Changed line 66 to use === for binary comparison
- Aligns with strict_types declaration
- Improves type safety

Author: claude

src/Serializer.php

@@ -63,7 +63,7 @@ public function serializeHar(Har $data): string
      */
     public function removeBOM(string $data): string
     {
-        if (substr($data, 0, 3) == pack('CCC', 0xEF, 0xBB, 0xBF)) {
+        if (substr($data, 0, 3) === pack('CCC', 0xEF, 0xBB, 0xBF)) {
             $data = substr($data, 3);
         }