docs: improve docs

Author: zepfred

core/src/main/java/ai/timefold/solver/core/api/solver/SolverJobBuilder.java

@@ -59,6 +59,10 @@ public interface SolverJobBuilder<Solution_, ProblemId_> {
 
     /**
      * Sets the best solution consumer, which may be called multiple times during the solving process.
+     * <p>
+     * We strongly recommend not applying any changes to the solution instance while the solver runs.
+     * It is essential to understand that the solution instance is not cloned when the event is triggered,
+     * and any modifications may lead to inconsistencies due to its internal reuse.
      *
      * @param bestSolutionConsumer called multiple times for each new best solution on a consumer thread
      * @return this