docs: add @deprecated guidance to two deprecated event setters

PiperOrigin-RevId: 990262251

Author: kvmilos

core/src/main/java/com/google/adk/events/Event.java

@@ -172,6 +172,12 @@ public void setErrorCode(@Nullable FinishReason errorCode) {
     this.errorCode = errorCode;
   }
 
+  /**
+   * Sets the finish reason from an {@link Optional}.
+   *
+   * @deprecated Use {@link #setFinishReason(FinishReason)} with {@code finishReason.orElse(null)}
+   *     instead.
+   */
   @Deprecated
   @SuppressWarnings("checkstyle:IllegalType")
   public void setFinishReason(Optional<FinishReason> finishReason) {

core/src/main/java/com/google/adk/events/EventActions.java

@@ -92,7 +92,13 @@ public Map<String, Object> stateDelta() {
     return stateDelta;
   }
 
-  @Deprecated // Use stateDelta() and removeStateByKey() instead.
+  /**
+   * Replaces the state delta.
+   *
+   * @deprecated Update the map returned by {@link #stateDelta()} instead, and use {@link
+   *     #removeStateByKey(String)} to remove a key.
+   */
+  @Deprecated
   public void setStateDelta(ConcurrentMap<String, Object> stateDelta) {
     this.stateDelta = stateDelta;
   }