[Bug]: waitForCondition exhaustion can produce FAILED invocation without ErrorObject

Expected Behavior

When waitForCondition exhausts its configured attempts, the SDK should:

1. Checkpoint the WaitForCondition step as FAILED with a non-null ErrorObject.
2. Checkpoint an enclosing synchronous child context as FAILED with a non-null ErrorObject.
3. Return a root DurableExecutionInvocationOutput with Status=FAILED and a non-null ErrorObject.

This ensures replay preserves useful diagnostics and any service/emulator consuming the invocation result can reliably record the execution as failed.

Actual Behavior

The built-in wait strategies throw WaitForConditionFailedException(String), whose DurableOperationException state has a null ErrorObject.

That null propagates through the failure path:

• WaitForConditionOperation.handleCheckFailure() reuses DurableOperationException.getErrorObject() without a null fallback.
• ChildContextOperation.handleChildContextFailure() does the same.
• DurableExecutor.buildErrorObject() returns DurableOperationException.getErrorObject() directly, even when it is null.

The final invocation output can therefore be equivalent to:

{
  "Status": "FAILED"
}

The Java LocalDurableTestRunner preserves the FAILED status, but the error is absent. When used through SAM Local, this combines with an emulator bug that currently converts FAILED with no error into ExecutionSucceeded.

Steps to Reproduce

Use a synchronous child context containing a condition that never stops polling:

var runner = LocalDurableTestRunner.create(String.class, (input, ctx) ->
        ctx.runInChildContext("child", String.class, child ->
                child.waitForCondition(
                        "poll",
                        String.class,
                        (state, stepCtx) -> WaitForConditionResult.continuePolling(state),
                        WaitForConditionConfig.<String>builder()
                                .waitStrategy(WaitStrategies.fixedDelay(
                                        2, Duration.ofSeconds(1)))
                                .build())));

var result = runner.runUntilComplete("test");

The local runner reports FAILED, but the root error is absent. Running the equivalent handler through SAM Local can produce this history:

StepFailed (WaitForCondition)
ContextFailed (RunInChildContext)
InvocationCompleted
ExecutionSucceeded

SDK Version

2.1.0; the behavior is also present on current 2.1.1-SNAPSHOT / main as of 2026-08-19.

Java Version

17

Is this a regression?

No known working version.

Last Working Version

N/A

Proposed Fix

Always fall back to serializing the thrown exception when an SDK exception has no embedded error:

if (e instanceof DurableOperationException operationException
        && operationException.getErrorObject() != null) {
    return operationException.getErrorObject();
}
return ExceptionHelper.buildErrorObject(e, serDes);

Apply equivalent null fallbacks when checkpointing failures in WaitForConditionOperation and ChildContextOperation, so operation history and replay also retain the error.

Add an integration test for max-attempt exhaustion inside synchronous runInChildContext that asserts:

• the step is failed with error details;
• the child context is failed with error details;
• the root invocation is FAILED with an error.

Related Issue

The SAM Local emulator status-handling defect exposed by this null error is tracked in aws/aws-durable-execution-sdk-python#656.

先从 WaitForConditionOperation.handleCheckFailure()、ChildContextOperation.handleChildContextFailure() 和 DurableExecutor.buildErrorObject() 入手，然后使用 LocalDurableTestRunner 运行 runInChildContext 的同步复现。添加 null-error 回退，并添加一个覆盖最大尝试次数耗尽的集成测试。当 step、child context 和 root invocation 全部为 FAILED 且包含错误详情时，即表示完成。