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/appsettings.json

@@ -0,0 +1,79 @@
+{
+  "Logging": {
+    "LogLevel": {
+      "Default": "Information",
+      "Microsoft.AspNetCore": "Warning"
+    }
+  },
+  "AllowedHosts": "*",
+  "MxGateway": {
+    "Authentication": {
+      "Mode": "ApiKey",
+      "SqlitePath": "C:\\ProgramData\\MxGateway\\gateway-auth.db",
+      "PepperSecretName": "MxGateway:ApiKeyPepper",
+      "RunMigrationsOnStartup": true
+    },
+    "Ldap": {
+      "Enabled": true,
+      "Server": "localhost",
+      "Port": 3893,
+      "UseTls": false,
+      "AllowInsecureLdap": true,
+      "SearchBase": "dc=lmxopcua,dc=local",
+      "ServiceAccountDn": "cn=serviceaccount,dc=lmxopcua,dc=local",
+      "ServiceAccountPassword": "serviceaccount123",
+      "UserNameAttribute": "cn",
+      "DisplayNameAttribute": "cn",
+      "GroupAttribute": "memberOf",
+      "RequiredGroup": "GwAdmin"
+    },
+    "Worker": {
+      "ExecutablePath": "src\\ZB.MOM.WW.MxGateway.Worker\\bin\\x86\\Release\\ZB.MOM.WW.MxGateway.Worker.exe",
+      "RequiredArchitecture": "X86",
+      "StartupTimeoutSeconds": 30,
+      "ShutdownTimeoutSeconds": 10,
+      "HeartbeatIntervalSeconds": 5,
+      "HeartbeatGraceSeconds": 15,
+      "MaxMessageBytes": 16777216
+    },
+    "Sessions": {
+      "DefaultCommandTimeoutSeconds": 30,
+      "MaxSessions": 64,
+      "MaxPendingCommandsPerSession": 128,
+      "DefaultLeaseSeconds": 1800,
+      "LeaseSweepIntervalSeconds": 30,
+      "AllowMultipleEventSubscribers": false
+    },
+    "Events": {
+      "QueueCapacity": 10000,
+      "BackpressurePolicy": "FailFast"
+    },
+    "Dashboard": {
+      "Enabled": true,
+      "PathBase": "/dashboard",
+      "RequireAdminScope": true,
+      "AllowAnonymousLocalhost": true,
+      "SnapshotIntervalMilliseconds": 1000,
+      "RecentFaultLimit": 100,
+      "RecentSessionLimit": 200,
+      "ShowTagValues": false
+    },
+    "Protocol": {
+      "WorkerProtocolVersion": 1,
+      "MaxGrpcMessageBytes": 16777216
+    },
+    "Galaxy": {
+      "ConnectionString": "Server=localhost;Database=ZB;Integrated Security=True;TrustServerCertificate=True;Encrypt=False;",
+      "CommandTimeoutSeconds": 60,
+      "DashboardRefreshIntervalSeconds": 30,
+      "PersistSnapshot": true,
+      "SnapshotCachePath": "C:\\ProgramData\\MxGateway\\galaxy-snapshot.json"
+    },
+    "Alarms": {
+      "Enabled": true,
+      "SubscriptionExpression": "\\\\DESKTOP-6JL3KKO\\Galaxy!DEV",
+      "DefaultArea": "",
+      "ReconcileIntervalSeconds": 30
+    }
+  }
+}