Configure default SSH shell with precedence: PS7 > PS5 > unchanged

- Checks for PowerShell 7 at Program Files\PowerShell\7\pwsh.exe
- Falls back to PowerShell 5 at System32\WindowsPowerShell\v1.0\powershell.exe
- Leaves default shell unchanged if neither found
- Sets HKLM\SOFTWARE\OpenSSH\DefaultShell registry value
- Sets DefaultShellCommandOption to '-NoLogo -NoProfile -Command'
- Idempotent: only updates registry if value differs

Invoke-OpenSSHConfiguration.ps1

@@ -928,6 +928,81 @@ Switch (Test-ProcessElevationStatus)
                                     }
                                 #endregion
 
+                                #region Configure Default Shell (PowerShell 7 > PowerShell 5 > No Change)
+                                  $OpenSSHRegistryPath = 'HKLM:\SOFTWARE\OpenSSH'
+
+                                  #Check for PowerShell 7 first, then PowerShell 5
+                                  $PowerShell7Path = [System.IO.FileInfo]"$($Env:ProgramFiles)\PowerShell\7\pwsh.exe"
+                                  $PowerShell5Path = [System.IO.FileInfo]"$($Env:SystemRoot)\System32\WindowsPowerShell\v1.0\powershell.exe"
+
+                                  $DefaultShellPath = $Null
+                                  $DefaultShellCommandOption = $Null
+
+                                  Switch ($True)
+                                    {
+                                        {($PowerShell7Path.Exists -eq $True)}
+                                          {
+                                              $DefaultShellPath = $PowerShell7Path.FullName
+                                              $DefaultShellCommandOption = '-NoLogo -NoProfile -Command'
+                                              $WriteLogMessage.Invoke(0, @("PowerShell 7 detected at `"$($DefaultShellPath)`"."))
+                                          }
+
+                                        {($PowerShell5Path.Exists -eq $True)}
+                                          {
+                                              $DefaultShellPath = $PowerShell5Path.FullName
+                                              $DefaultShellCommandOption = '-NoLogo -NoProfile -Command'
+                                              $WriteLogMessage.Invoke(0, @("PowerShell 5 detected at `"$($DefaultShellPath)`"."))
+                                          }
+
+                                        Default
+                                          {
+                                              $WriteLogMessage.Invoke(1, @("No PowerShell installation detected. Leaving default shell unchanged."))
+                                          }
+                                    }
+
+                                  Switch ($Null -ine $DefaultShellPath)
+                                    {
+                                        {($_ -eq $True)}
+                                          {
+                                              #Ensure OpenSSH registry key exists
+                                              Switch (Test-Path -Path $OpenSSHRegistryPath -ErrorAction SilentlyContinue)
+                                                {
+                                                    {($_ -eq $False)}
+                                                      {
+                                                          $WriteLogMessage.Invoke(0, @("Creating OpenSSH registry key. Please Wait..."))
+                                                          $Null = New-Item -Path $OpenSSHRegistryPath -Force -ErrorAction SilentlyContinue
+                                                      }
+                                                }
+
+                                              #Get current values
+                                              $CurrentDefaultShell = Get-ItemProperty -Path $OpenSSHRegistryPath -Name 'DefaultShell' -ErrorAction SilentlyContinue | Select-Object -ExpandProperty 'DefaultShell' -ErrorAction SilentlyContinue
+                                              $CurrentDefaultShellCommandOption = Get-ItemProperty -Path $OpenSSHRegistryPath -Name 'DefaultShellCommandOption' -ErrorAction SilentlyContinue | Select-Object -ExpandProperty 'DefaultShellCommandOption' -ErrorAction SilentlyContinue
+
+                                              #Set DefaultShell if different
+                                              Switch ($CurrentDefaultShell -ine $DefaultShellPath)
+                                                {
+                                                    {($_ -eq $True)}
+                                                      {
+                                                          $WriteLogMessage.Invoke(0, @("Setting default shell to `"$($DefaultShellPath)`". Please Wait..."))
+                                                          $Null = Set-ItemProperty -Path $OpenSSHRegistryPath -Name 'DefaultShell' -Value $DefaultShellPath -Type String -Force -ErrorAction SilentlyContinue
+                                                          $WriteLogMessage.Invoke(0, @("Default shell configured."))
+                                                      }
+                                                }
+
+                                              #Set DefaultShellCommandOption if different
+                                              Switch ($CurrentDefaultShellCommandOption -ine $DefaultShellCommandOption)
+                                                {
+                                                    {($_ -eq $True)}
+                                                      {
+                                                          $WriteLogMessage.Invoke(0, @("Setting default shell command option to `"$($DefaultShellCommandOption)`". Please Wait..."))
+                                                          $Null = Set-ItemProperty -Path $OpenSSHRegistryPath -Name 'DefaultShellCommandOption' -Value $DefaultShellCommandOption -Type String -Force -ErrorAction SilentlyContinue
+                                                          $WriteLogMessage.Invoke(0, @("Default shell command option configured."))
+                                                      }
+                                                }
+                                          }
+                                    }
+                                #endregion
+
                                 #region Service Management (Automatic)
                                   $SSHDService = Get-Service -Name 'sshd' -ErrorAction SilentlyContinue