NOOP task: missing builder class

## Summary

`TaskType.NOOP` exists in the SDK enum but there is no `Noop` builder class in
`conductor-client/src/main/java/com/netflix/conductor/sdk/workflow/def/tasks/`.
Users cannot create a NOOP workflow task using the fluent SDK API — they must fall
back to constructing a raw `WorkflowTask` manually.

## Server baseline

Conductor **3.32.0-rc.9**

## Evidence

**Static:** `TaskType.NOOP` is in the enum; no `Noop.java` file exists under
`conductor-client/…/def/tasks/`.

**Live (2026-07-16):** A raw `WorkflowTask` with `"type": "NOOP"` was registered
and executed against Conductor OSS 3.32.0-rc.9 at `http://loki.local:8080`. The workflow
completed successfully, confirming the server supports NOOP — the gap is SDK-only.

## Expected behaviour

Users should be able to write:
```java
new Noop("noop_ref")
```

## Proposed fix

```java
public class Noop extends Task {
public Noop(String taskReferenceName) {
super(taskReferenceName, TaskType.NOOP);
}
}
```

No `updateWorkflowTask` override required — NOOP has no `inputParameters`.

## Related

Discovered during systematic SDK audit against Conductor OSS 3.32.0-rc.9 server.
Same gap exists in the Python SDK (conductor-oss/python-sdk#430).

Inizia in conductor-client/src/main/java/com/netflix/conductor/sdk/workflow/def/tasks/ e confronta le sottoclassi Task esistenti con TaskType.NOOP nell’enum dell’SDK. Esegui la build Java e i test del progetto dopo aver aggiunto il builder; il lavoro è completato quando gli utenti possono istanziare new Noop("noop_ref") e questo rappresenta un task di workflow NOOP senza costruire manualmente un WorkflowTask.

Scritto dal modello di indicizzazione a partire dal testo della issue.