Lower PowerShell version requirement to 3.0

Changed the script to require PowerShell 3.0 instead of 5.1 and updated the Key Vault secret retrieval to be compatible with PowerShell 3.0 by extracting the secret value using SecretValueText.

Author: potatoqualitee

gh-runners/init.ps1

@@ -1,4 +1,4 @@
-#Requires -Version 5.1
+#Requires -Version 3.0
 <#
 .SYNOPSIS
     GitHub Actions runner configuration script for Azure VMSS
@@ -61,14 +61,16 @@ try {
     Write-Log "  - VM Name: $($env:COMPUTERNAME)"
 
     Write-Log "Retrieving GitHub PAT from Key Vault..."
-    $GithubToken = Get-AzKeyVaultSecret `
+    $secretObj = Get-AzKeyVaultSecret `
         -VaultName $KeyVaultName `
-        -Name "GITHUB-RUNNER-TOKEN" `
-        -AsPlainText
+        -Name "GITHUB-RUNNER-TOKEN"
 
-    if (-not $GithubToken) {
+    if (-not $secretObj) {
         throw "Failed to retrieve GitHub token from Key Vault"
     }
+
+    # PS 3.0 compatible way to get plaintext secret
+    $GithubToken = $secretObj.SecretValueText
     Write-Log "GitHub PAT retrieved successfully"
 
     Write-Log "Requesting runner registration token from GitHub API..."