refactor(windows scripts): remove BOM and improve UTF-8 handling

windows/tools/net-diag.ps1

@@ -1,4 +1,4 @@
-<#
+<#
     LXS - Network Diagnostics (Windows)
     Description: Inspect and repair the network stack.
                  Everything is read-only except option 8 (stack reset).
@@ -20,7 +20,10 @@ if ($LxsLibPath -and (Test-Path $LxsLibPath)) {
         Write-Error 'Failed to fetch lib/common.ps1'
         exit 1
     }
-    . ([scriptblock]::Create($LxsLibSource))
+    # The library ships with a UTF-8 BOM (Windows PowerShell 5.1 needs it to
+    # read the file as UTF-8); over HTTP that BOM arrives as a leading U+FEFF
+    # character, which the parser will not accept.
+    . ([scriptblock]::Create(($LxsLibSource -replace '^\uFEFF', '')))
 }
 
 $env:LXS_LOG_FILE = Join-Path (Get-LxsTempDir) 'lxs_net_diag.log'
@@ -51,7 +54,8 @@ function Show-LxsListeningPorts {
     Write-Host ''
     try {
         $rows = Get-NetTCPConnection -State Listen -ErrorAction Stop | ForEach-Object {
-            $procName = try { (Get-Process -Id $_.OwningProcess -ErrorAction Stop).ProcessName } catch { 'unknown' }
+            $procName = 'unknown'
+            try { $procName = (Get-Process -Id $_.OwningProcess -ErrorAction Stop).ProcessName } catch { $procName = 'unknown' }
             [pscustomobject]@{
                 Local   = "$($_.LocalAddress):$($_.LocalPort)"
                 Port    = $_.LocalPort