Update UnbrandedGeneratorVersion to 1.0.0-alpha.20251006.1 (Azure#53027)

* Update UnbrandedGeneratorVersion to 1.0.0-alpha.20251006.1

* optionality tests

---------

Co-authored-by: Ubuntu <cloudtest@c9ce56e0c000001.tkkhlgj2u51eln3mcb0lygmbye.dx.internal.cloudapp.net>
Co-authored-by: jolov <[email protected]>

Author: 3 people

eng/Packages.Data.props

@@ -467,7 +467,7 @@
 
   <PropertyGroup>
     <TestProxyVersion>1.0.0-dev.20250930.1</TestProxyVersion>
-    <UnbrandedGeneratorVersion>1.0.0-alpha.20251002.1</UnbrandedGeneratorVersion>
+    <UnbrandedGeneratorVersion>1.0.0-alpha.20251006.1</UnbrandedGeneratorVersion>
     <AzureGeneratorVersion>1.0.0-alpha.20250929.3</AzureGeneratorVersion>
   </PropertyGroup>
 </Project>

eng/http-client-csharp-emitter-package-lock.json

@@ -2,7 +2,7 @@
   "main": "dist/src/index.js",
   "dependencies": {
     "client-plugin": "file:../../../../eng/packages/plugins/client",
-    "@typespec/http-client-csharp": "1.0.0-alpha.20251002.1"
+    "@typespec/http-client-csharp": "1.0.0-alpha.20251006.1"
   },
   "devDependencies": {
     "@azure-tools/typespec-client-generator-core": "0.60.0",