fix(client): force JSON for parsed exec

Author: loong10k

src/main/java/io/github/easy4j/codex/CodexClient.java

@@ -161,7 +161,7 @@ public CodexCliResult exec(CodexCli.ExecOptions opts) {
      *         empty or unparseable.
      */
     public List<CodexEvent> execAndParse(String prompt) {
-        CodexCliResult result = exec(prompt);
+        CodexCliResult result = exec(defaultOptions(prompt).json(true));
         return parseJsonlOutput(result.getStdout());
     }