feat(mesh): deployment_artifact.v1 proto + first in-repo Grpc.Tools codegen

The repo has consumed packaged gRPC clients (LocalDb.Replication,
HistorianGateway.Client) but never compiled a proto locally. This adds the
Grpc.Tools toolchain to Commons and a deployment_artifact.proto with a single
server-streaming Fetch(deployment_id) -> stream ArtifactChunk RPC, generating
both the server base and the client stub (GrpcServices="Both") so central
(Host/AdminUI) and the node (Runtime) share one reference. A compile-touch test
pins the codegen: it stops compiling if generation regresses.

Claude-Session: https://claude.ai/code/session_01GASWkNEi68FSCtvr6rLoEW

tests/Core/ZB.MOM.WW.OtOpcUa.Commons.Tests/DeploymentArtifactProtoTests.cs

@@ -0,0 +1,38 @@
+using Shouldly;
+using Xunit;
+using ZB.MOM.WW.OtOpcUa.Commons.Protos.DeploymentArtifact.V1;
+
+namespace ZB.MOM.WW.OtOpcUa.Commons.Tests;
+
+/// <summary>
+///     A compile-touch test: it exists so that the repo's first locally-compiled proto
+///     (<c>deployment_artifact.proto</c>) is proven to generate both the client stub and the server
+///     base and the message types. If Grpc.Tools codegen regresses, this file stops compiling —
+///     which, under TreatWarningsAsErrors, breaks the build loudly rather than silently.
+/// </summary>
+public class DeploymentArtifactProtoTests
+{
+    [Fact]
+    public void The_request_message_carries_the_deployment_id()
+    {
+        var request = new FetchRequest { DeploymentId = "abc" };
+
+        request.DeploymentId.ShouldBe("abc");
+    }
+
+    [Fact]
+    public void The_chunk_message_carries_bytes()
+    {
+        var chunk = new ArtifactChunk { Data = Google.Protobuf.ByteString.CopyFromUtf8("x") };
+
+        chunk.Data.Length.ShouldBe(1);
+    }
+
+    [Fact]
+    public void The_service_base_and_client_types_generate()
+    {
+        // Referencing these types is the whole assertion — GrpcServices="Both" must emit both.
+        typeof(DeploymentArtifactService.DeploymentArtifactServiceBase).ShouldNotBeNull();
+        typeof(DeploymentArtifactService.DeploymentArtifactServiceClient).ShouldNotBeNull();
+    }
+}