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>

docs/AlarmClientDiscovery.md

@@ -1,7 +1,7 @@
 # aaAlarmManagedClient discovery — public surface, 2026-05-01
 
 Result of running
-`MxGateway.Worker.Tests.AlarmClientDiscoveryTests.DumpAlarmClientPublicSurface`
+`ZB.MOM.WW.MxGateway.Worker.Tests.AlarmClientDiscoveryTests.DumpAlarmClientPublicSurface`
 against the deployed AVEVA assembly:
 
 - File:
@@ -68,7 +68,7 @@ list.
 ## What this means
 
 The architecture comment on
-`src/MxGateway.Worker/MxAccess/AlarmClientConsumer.cs` (PR A.5) is
+`src/ZB.MOM.WW.MxGateway.Worker/MxAccess/AlarmClientConsumer.cs` (PR A.5) is
 **wrong against this deployed assembly**:
 
 > "The AVEVA alarm-manager surface (`IAlarmMgrDataProvider`) exposes
@@ -89,7 +89,7 @@ never gets invoked at runtime. Until A.2 lands a WM_APP pump,
 
 ## Live runtime probe — 2026-05-01
 
-`MxGateway.Worker.Tests.AlarmClientWmProbeTests.ProbeAlarmClientWmMessages`
+`ZB.MOM.WW.MxGateway.Worker.Tests.AlarmClientWmProbeTests.ProbeAlarmClientWmMessages`
 is a Skip-gated runtime probe that creates a real message-only
 window, calls `AlarmClient.RegisterConsumer(hWnd, …)` +
 `Subscribe(@"\Galaxy!", …)`, and pumps for 20s while logging every
@@ -505,7 +505,7 @@ Interop.WNWRAPCONSUMERLib.dll`). The COM class is registered in
 Apartment` — `new wwAlarmConsumerClass()` succeeds via
 `CoCreateInstance`.
 
-The probe `MxGateway.Worker.Tests/WnWrapConsumerProbeTests.cs`
+The probe `ZB.MOM.WW.MxGateway.Worker.Tests/WnWrapConsumerProbeTests.cs`
 (Skip-gated, archival) drove the captured run. Lifecycle:
 
 1. `new wwAlarmConsumerClass()` — instantiated.
@@ -622,7 +622,7 @@ Replacing `aaAlarmManagedClient.AlarmClient` with
 alarm-consumer surface unblocks A.2 fully. Outline:
 
 1. **Reference path:** drop `aaAlarmManagedClient.dll` reference
-   from `MxGateway.Worker.csproj`; add `Interop.WNWRAPCONSUMERLib.dll`
+   from `ZB.MOM.WW.MxGateway.Worker.csproj`; add `Interop.WNWRAPCONSUMERLib.dll`
    reference from `mxaccessgw/lib/`. (Or commit the interop dll
    in-tree under `lib/` and reference relatively.)
 2. **`AlarmClientConsumer` → `WnWrapAlarmConsumer`:** rewrite