fix(java): picocli ParameterException for browse --depth; warn on --parent 0

Replaces the raw IllegalArgumentException thrown by GalaxyBrowseCommand for
--depth < 0 with a CommandLine.ParameterException so picocli surfaces a clean
single-line error instead of an unhandled stack trace. Adds an upper bound of
50 (matching the Python client) so --depth > 50 is also rejected cleanly.

Emits a stderr warning when --parent 0 is supplied explicitly, matching
Go/Rust client behaviour, because gobject id 0 is the server's root-walk
sentinel and passing it via --parent is almost always a mistake.

Adds three new tests: negative depth, depth > 50, and the --parent 0 warning path.

src/ZB.MOM.WW.MxGateway.Tests/Gateway/Workers/Fakes/FakeWorkerHarness.cs

@@ -409,6 +409,37 @@ public sealed class FakeWorkerHarness : IAsyncDisposable
         CancellationToken cancellationToken = default)
     {
         WorkerEnvelope commandEnvelope = await ReadCommandAsync(cancellationToken).ConfigureAwait(false);
+        return await RespondToControlCommandAsync(commandEnvelope, cancellationToken).ConfigureAwait(false);
+    }
+
+    /// <summary>
+    /// Accepts an already-read command envelope and, if it is one of the five control
+    /// command kinds (Ping, GetSessionState, GetWorkerInfo, DrainEvents, ShutdownWorker),
+    /// writes a canned reply that mirrors the real worker's reply shape. For ShutdownWorker
+    /// the method additionally sends a <see cref="WorkerShutdownAck"/> after the OK reply.
+    /// Use this overload when the caller has already consumed the envelope from the pipe
+    /// (e.g., to inspect the kind before routing) to avoid re-reading.
+    /// </summary>
+    /// <param name="commandEnvelope">The already-read command envelope to respond to.</param>
+    /// <param name="cancellationToken">Token to cancel the asynchronous operation.</param>
+    /// <returns>The command envelope that was handled.</returns>
+    /// <exception cref="ArgumentException">
+    /// Thrown when <paramref name="commandEnvelope"/> does not contain a <c>WorkerCommand</c>.
+    /// </exception>
+    /// <exception cref="InvalidOperationException">
+    /// Thrown when the command kind is not one of the five control command kinds.
+    /// </exception>
+    public async Task<WorkerEnvelope> RespondToControlCommandAsync(
+        WorkerEnvelope commandEnvelope,
+        CancellationToken cancellationToken = default)
+    {
+        if (commandEnvelope.BodyCase != WorkerEnvelope.BodyOneofCase.WorkerCommand)
+        {
+            throw new ArgumentException(
+                $"Expected WorkerCommand envelope but received {commandEnvelope.BodyCase}.",
+                nameof(commandEnvelope));
+        }
+
         MxCommand command = commandEnvelope.WorkerCommand.Command;
 
         switch (command.Kind)