[Bug]: Emulator retries invalid invocation outputs that the service fails immediately

### Expected Behavior

The emulator should mirror the service's handling of invalid invocation outputs. Verified service behavior:

Most invalid outputs **fail the execution immediately, with no retry**. This applies to:

- `Status=FAILED` with a `Result` present
- `Status=SUCCEEDED` with an `Error` present
- a missing or unrecognized `Status`
- an unparseable/malformed invocation output payload

In each case the service fails the execution with an error object of the form:

```json
{
"ErrorType": "InvalidParameterValueException",
"ErrorMessage": ""
}
```

There is exactly **one retried case**: `Status=PENDING` when the execution has no pending operations. The service treats this as a transient runtime-level error (it can arise from SDK race conditions that resolve on replay) and retries the invocation, up to 3 consecutive attempts, before failing the execution with the same `InvalidParameterValueException`-shaped error.

### Actual Behavior

In `aws_durable_execution_sdk_python_testing.executor.Executor._finish_invocation()`, **all** validation failures from `_validate_invocation_response_and_store()` are routed through the same retry path:

```python
except (InvalidParameterValueException, IllegalStateException) as e:
...
self._set_invocation_gate(execution_arn, InvocationState.PRE_INVOKE)
self._retry_invocation(execution, error_obj)
return
```

`_retry_invocation` re-invokes the handler up to `MAX_CONSECUTIVE_FAILED_ATTEMPTS = 5` times with a flat `RETRY_BACKOFF_SECONDS = 5` backoff before failing.

Consequences:

- A deterministically invalid output (e.g. `SUCCEEDED` with an `Error`) is re-invoked 5 times before failing, where the service fails on the first response. For a deterministic handler this adds ~25 seconds and 4 pointless invocations, and every re-invocation replays the handler.
- The one case the service *does* retry (`PENDING` with no pending operations) gets 5 attempts instead of 3.
- The terminal error surfaced to the customer is `ErrorObject.from_exception(e)` rather than the service's `{ErrorType: "InvalidParameterValueException", ErrorMessage: ...}` shape.

### Proposed Fix

In `_finish_invocation`, distinguish the two classes:

- Fail-fast validation errors (`FAILED`+`Result`, `SUCCEEDED`+`Error`, missing/unknown status, malformed output): fail the execution immediately with an `InvalidParameterValueException`-typed error object carrying the validation message.
- `PENDING` with no pending operations: keep the retry path, with a consecutive-attempt cap of 3.

Regression tests:

- each fail-fast case produces a FAILED execution after a **single** invocation, with the `InvalidParameterValueException` error shape;
- `PENDING` with no pending operations retries and fails after 3 consecutive attempts;
- a transient case (invalid output once, then a valid `PENDING`/`SUCCEEDED`) recovers without failing the execution.

### Related

- Found while investigating https://github.com/aws/aws-durable-execution-sdk-python/issues/656 (FAILED without ErrorObject completed as SUCCEEDED by local emulator). This issue covers the adjacent divergence in the same code path: how invalid outputs are retried vs. failed.

### SDK Version

`aws-durable-execution-sdk-python-testing` current `main` as of 2026-08-21.

### Python Version

3.13

### Is this a regression?

No known working version.

Beginne in aws_durable_execution_sdk_python_testing.executor.Executor._finish_invocation() und verfolge _validate_invocation_response_and_store() sowie _retry_invocation(). Reproduziere die aufgeführten Fälle ungültiger Ausgaben und den PENDING-Fall und füge anschließend Regressionstests hinzu, die das Fail-fast-Verhalten, die Fehlerstruktur InvalidParameterValueException, eine Obergrenze von drei Versuchen für PENDING und die Erholung nach einer vorübergehenden ungültigen Ausgabe zeigen.

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