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/GatewayProcessDesign.md

@@ -59,7 +59,7 @@ Those belong to the worker.
 ## High-Level Components
 
 ```text
-MxGateway.Server
+ZB.MOM.WW.MxGateway.Server
   Program / Host
   Configuration
   Grpc
@@ -677,7 +677,7 @@ development only.
 Dashboard authentication reuses the API-key verifier and scope model. The
 dashboard login endpoint accepts the key in a form post, checks `admin` scope
 when `Dashboard:RequireAdminScope` is enabled, and signs in with the
-`MxGateway.Dashboard` cookie scheme. The cookie is HTTP-only, secure, strict
+`ZB.MOM.WW.MxGateway.Dashboard` cookie scheme. The cookie is HTTP-only, secure, strict
 SameSite, and scoped with the `__Host-MxGatewayDashboard` name. Logout clears
 that cookie. Login and logout posts use anti-forgery validation, and dashboard
 API keys are not accepted in query strings. `Dashboard:AllowAnonymousLocalhost`
@@ -703,15 +703,15 @@ gRPC admin API. It should initialize the auth database, create keys, list keys
 without secrets, revoke keys, rotate keys, and print raw secrets only once at
 creation.
 
-`MxGateway.Server` exposes local API-key administration as an `apikey`
+`ZB.MOM.WW.MxGateway.Server` exposes local API-key administration as an `apikey`
 subcommand before the web host starts:
 
 ```bash
-MxGateway.Server apikey init-db --sqlite-path C:\ProgramData\MxGateway\gateway-auth.db
-MxGateway.Server apikey create-key --key-id operator01 --display-name Operator --scopes session:open,events:read
-MxGateway.Server apikey list-keys --json
-MxGateway.Server apikey revoke-key --key-id operator01
-MxGateway.Server apikey rotate-key --key-id operator01 --json
+ZB.MOM.WW.MxGateway.Server apikey init-db --sqlite-path C:\ProgramData\MxGateway\gateway-auth.db
+ZB.MOM.WW.MxGateway.Server apikey create-key --key-id operator01 --display-name Operator --scopes session:open,events:read
+ZB.MOM.WW.MxGateway.Server apikey list-keys --json
+ZB.MOM.WW.MxGateway.Server apikey revoke-key --key-id operator01
+ZB.MOM.WW.MxGateway.Server apikey rotate-key --key-id operator01 --json
 ```
 
 The subcommands accept `--sqlite-path`, `--pepper`, and `--json`. `--pepper`
@@ -846,7 +846,7 @@ Suggested configuration shape:
       "RunMigrationsOnStartup": true
     },
     "Worker": {
-      "ExecutablePath": "src/MxGateway.Worker/bin/x86/Release/MxGateway.Worker.exe",
+      "ExecutablePath": "src/ZB.MOM.WW.MxGateway.Worker/bin/x86/Release/ZB.MOM.WW.MxGateway.Worker.exe",
       "WorkingDirectory": null,
       "RequiredArchitecture": "X86",
       "StartupTimeoutSeconds": 30,
@@ -887,7 +887,7 @@ Suggested configuration shape:
 
 Do not scatter connection or path constants through implementation code.
 
-`MxGateway.Server` binds this section to `GatewayOptions` at startup and
+`ZB.MOM.WW.MxGateway.Server` binds this section to `GatewayOptions` at startup and
 registers validation with `ValidateOnStart()`. Startup fails before the gateway
 begins serving traffic when required authentication settings are missing,
 timeouts or queue sizes are not positive, dashboard settings are malformed, or