Merged PR 38899: Fix signing for .nupkg

Fix signing for .nupkg, defining ADO variable

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#### AI description  (iteration 1)
#### PR Classification
Bug fix to resolve issues with signing .nupkg packages in the pipeline.

#### PR Summary
This pull request adjusts the pipeline steps to ensure the correct directory path is used for signing the .nupkg, while adding debugging steps to verify the directory contents before and after signing.
- `/pipelines/PSResourceGet-Official.yml`: Introduces a `publishPath` variable using `Join-Path` to reliably point to the `PublishedNupkg` directory.
- `/pipelines/PSResourceGet-Official.yml`: Updates registration, signing, and directory navigation steps to use `publishPath` instead of hardcoded paths, and adds commands to output folder contents for debugging.
<!-- GitOpsUserAgent=GitOps.Apps.Server.pullrequestcopilot -->

Author: Anam Navied

.pipelines/PSResourceGet-Official.yml

@@ -234,25 +234,34 @@ extends:
             Import-Module -Name Microsoft.PowerShell.PSResourceGet -Force
 
             Set-Location "$(signOutPath)\Microsoft.PowerShell.PSResourceGet"
-            $null = New-Item -ItemType Directory -Path "$(signOutPath)\PublishedNupkg" -Force
+            $publishPath = Join-Path $(signOutPath) -ChildPath 'PublishedNupkg'
 
-            Register-PSResourceRepository -Name 'localRepo' -Uri "$(signOutPath)\PublishedNupkg"
+            $null = New-Item -ItemType Directory -Path $publishPath -Force
+
+            Register-PSResourceRepository -Name 'localRepo' -Uri $publishPath
             Publish-PSResource -Path "$(signOutPath)\Microsoft.PowerShell.PSResourceGet" -Repository 'localRepo' -Verbose
+            Write-Output "##vso[task.setvariable variable=publishPath;isOutput=true]$publishPath"
           displayName: Create nupkg for publishing
 
+        - pwsh: |
+            Set-Location '$(publishPath)'
+            Write-Host "Contents of signOutPath:"
+            Get-ChildItem '$(publishPath)' -Recurse
+          displayName: Find Nupkg Pre Signing
+
         - task: onebranch.pipeline.signing@1
           displayName: Sign nupkg
           inputs:
             command: 'sign'
             signing_profile: external_distribution
             files_to_sign: '**\*.nupkg'
-            search_root: "$(signOutPath)\PublishedNupkg"
+            search_root: '$(publishPath)'
 
         - pwsh: |
-            Set-Location "$(signOutPath)\PublishedNupkg"
+            Set-Location '$(publishPath)'
             Write-Host "Contents of signOutPath:"
-            Get-ChildItem "$(signOutPath)" -Recurse
-          displayName: Find Nupkg
+            Get-ChildItem '$(publishPath)' -Recurse
+          displayName: Find Nupkg Post Signing
 
         - task: CopyFiles@2
           displayName: "Copy nupkg to ob_outputDirectory - '$(ob_outputDirectory)'"