fix: expose LlmAgent's max steps parameter via a getter

PiperOrigin-RevId: 778557271

Author: google-genai-bot

core/src/main/java/com/google/adk/agents/LlmAgent.java

@@ -703,6 +703,10 @@ public boolean planning() {
     return planning;
   }
 
+  public Optional<Integer> maxSteps() {
+    return maxSteps;
+  }
+
   public Optional<GenerateContentConfig> generateContentConfig() {
     return generateContentConfig;
   }