fix(scripts): harden stop_netx and tweak start_netx

- Add timeout around Get-NetTCPConnection to avoid hangs; filter invalid PIDs; exit 0 on completion.
- Minor start_netx adjustments.

Co-authored-by: Cursor <cursoragent@cursor.com>

scripts/start_netx.ps1

@@ -91,6 +91,8 @@ if ($Background) {
         Write-Host "Log = $webLogFile"
         Write-Host "Err = $webErrFile"
     }
+    Write-Host ""
+    Write-Host "==> Background services started; this script exits (API/web keep running)." -ForegroundColor Cyan
     exit 0
 }