rename: prefix gateway projects/namespaces with ZB.MOM.WW + sln→slnx

Apply the ZB.MOM.WW. prefix to all gateway-side projects, folders,
.csproj/.sln contents, C# namespaces, using directives, generated proto
C# (csharp_namespace + checked-in generated files), InternalsVisibleTo
attributes, project-name string literals (LoadProject, .sln lookups,
worker exe paths, staticwebassets manifest), and the install/script/doc
references that point at any of the above. Migrate the solution from
.sln to .slnx via `dotnet sln migrate` and delete the old file.

External-runtime identifiers are intentionally NOT prefixed so external
configuration keeps working:
- GatewayMetrics.cs MeterName ("MxGateway.Server")
- DashboardAuthenticationDefaults Scheme/Policy ("MxGateway.Dashboard")
- GatewayRequestLoggingMiddleware logger category ("MxGateway.Request")
- StaRuntime thread name ("MxGateway.Worker.STA")
- appsettings.json root section "MxGateway" + env-var prefix
  MxGateway__... and secret-name MxGateway:ApiKeyPepper
- C:\ProgramData\MxGateway\ data dir paths

Also fixes two tests that were not rename-related but became visible
while validating the rename:

- WorkerLiveMxAccessSmokeTests.ShutDownAsync: cancellation that the
  gateway service correctly maps to RpcException(Cancelled) per gRPC
  convention was being misclassified as a stream fault. Added a sibling
  catch on RpcException with StatusCode.Cancelled.

- IntegrationTestEnvironment.ResolveRepositoryRoot: extracted IsRepositoryRoot
  and made it accept either a .git marker OR a .sln/.slnx next to src/
  so the worker-exe walker works in non-git working copies.

clients/proto/proto-inputs.json's protoRoot updated to point at
src/ZB.MOM.WW.MxGateway.Contracts/Protos.

Verified by `dotnet build` and a full `dotnet test` of the .slnx with
MXGATEWAY_RUN_LIVE_{MXACCESS,LDAP,GALAXY}_TESTS=1:
  Tests: 472/472 pass
  Worker.Tests: 280/280 pass (4 dev-rig [Fact(Skip=...)] skipped)
  IntegrationTests: 18/18 pass

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

src/ZB.MOM.WW.MxGateway.Server/Security/Authorization/GatewayScopes.cs

@@ -0,0 +1,37 @@
+namespace ZB.MOM.WW.MxGateway.Server.Security.Authorization;
+
+public static class GatewayScopes
+{
+    public const string SessionOpen = "session:open";
+    public const string SessionClose = "session:close";
+    public const string InvokeRead = "invoke:read";
+    public const string InvokeWrite = "invoke:write";
+    public const string InvokeSecure = "invoke:secure";
+    public const string EventsRead = "events:read";
+    public const string MetadataRead = "metadata:read";
+    public const string Admin = "admin";
+
+    /// <summary>
+    ///     The complete catalog of canonical scope strings the gateway authorization
+    ///     resolver recognizes. Key-creation paths (CLI and dashboard) validate requested
+    ///     scopes against this set so a typo or non-canonical name cannot persist a key
+    ///     whose scope strings the resolver never matches.
+    /// </summary>
+    public static readonly IReadOnlySet<string> All = new HashSet<string>(
+        [
+            SessionOpen,
+            SessionClose,
+            InvokeRead,
+            InvokeWrite,
+            InvokeSecure,
+            EventsRead,
+            MetadataRead,
+            Admin,
+        ],
+        System.StringComparer.Ordinal);
+
+    /// <summary>Determines whether the supplied scope string is a recognized canonical scope.</summary>
+    /// <param name="scope">Scope string to check.</param>
+    /// <returns><see langword="true"/> when the scope is canonical; otherwise <see langword="false"/>.</returns>
+    public static bool IsKnown(string scope) => All.Contains(scope);
+}