Merge Steam P2P multiplayer with character menu and map transitions

scripts/launch-multiplayer-test.ps1

@@ -0,0 +1,48 @@
+param([switch]$MenuOnly, [string]$MapPath = '', [switch]$TwoControllers, [ValidateRange(2,10)][int]$Players = 2, [string]$BuildDirectory = 'bin/multiplayer')
+$ErrorActionPreference = 'Stop'
+$instanceCount = if ($MenuOnly) { 1 } else { $Players }
+$workspace = Split-Path -Parent $PSScriptRoot
+$binary = Join-Path (Join-Path $workspace $BuildDirectory) 'skate3-multiplayer.exe'
+$installation = 'C:/Users/Daddy/AppData/Local/Skate3RustEngine/installations/957f4f78db9b4f59959f10dff8ff6a84'
+$assets = Join-Path $installation 'assets'
+# Reuse the combined character asset view when this checkout has one prepared.
+$combinedAssets = Join-Path $workspace '.local/combined-customiser/assets'
+if (Test-Path -LiteralPath (Join-Path $combinedAssets 'private/game.json')) { $assets = $combinedAssets }
+$markerOverlay = Join-Path $workspace '.local/session-marker/overlay'
+if (Test-Path -LiteralPath (Join-Path $markerOverlay 'hud.json')) { $env:SKATE3_SESSION_MARKER_OVERLAY = $markerOverlay }
+if (-not (Test-Path -LiteralPath $binary)) { throw 'Build missing. Run BUILD-MULTIPLAYER-TEST.bat first.' }
+if (-not (Test-Path -LiteralPath (Join-Path $assets 'private/game.json'))) { throw 'Prepared game assets are missing. No installer or conversion will be started.' }
+if (-not $MapPath) { $MapPath = Join-Path $installation 'maps/University.skate' }
+$MapPath = (Resolve-Path -LiteralPath $MapPath).Path
+if ([IO.Path]::GetExtension($MapPath) -ne '.skate') { throw 'Expected an existing .skate map.' }
+$logs = Join-Path $workspace ('logs/multiplayer/' + (Get-Date -Format 'yyyyMMdd-HHmmss') + '-' + [Guid]::NewGuid().ToString('N').Substring(0,8))
+New-Item -ItemType Directory -Path $logs -Force | Out-Null
+# Reserve distinct ports, then release immediately before the games start.
+$reservations = @(1..$instanceCount | ForEach-Object { [Net.Sockets.UdpClient]::new([Net.IPEndPoint]::new([Net.IPAddress]::Loopback,0)) })
+$ports = @($reservations | ForEach-Object { $_.Client.LocalEndPoint.Port })
+$session = Get-Random -Minimum 1 -Maximum ([long]::MaxValue)
+$reservations | ForEach-Object { $_.Dispose() }
+$common = '--assets "' + $assets + '" --map "' + $MapPath + '" --net-session ' + $session
+for ($index = 0; $index -lt $instanceCount; $index++) {
+    $label = [string][char](65 + $index)
+    $playerArgs = $common
+    if ($MenuOnly) {
+        # Start offline; Steam initializes only through the multiplayer menu.
+        $playerArgs += ' --start-paused'
+    } elseif ($index -eq 0) {
+        $playerArgs += ' --net-host 127.0.0.1:' + $ports[0]
+    } else {
+        $playerArgs += ' --net-local 127.0.0.1:' + $ports[$index] + ' 127.0.0.1:' + $ports[0]
+        # Guests advertise an unavailable outfit to exercise default fallback.
+        $playerArgs += ' --spawn-offset ' + ($index * 2).ToString([Globalization.CultureInfo]::InvariantCulture) + ' --appearance test-uninstalled-outfit'
+    }
+    $playerArgs += ' --player-title "Multiplayer ' + $label + ' - ' + $Players + ' player test"'
+    if ($TwoControllers -and $index -lt 2) { $playerArgs += ' --controller ' + $index }
+    $process = Start-Process -FilePath $binary -ArgumentList $playerArgs -WorkingDirectory $workspace -WindowStyle Normal -RedirectStandardOutput (Join-Path $logs ('player-' + $label.ToLower() + '.out.log')) -RedirectStandardError (Join-Path $logs ('player-' + $label.ToLower() + '.err.log')) -PassThru
+    Write-Host "Started player $label ($($process.Id))"
+}
+if ($MenuOnly) { Write-Host "Press Esc, then Multiplayer to host or browse Steam lobbies." }
+else { Write-Host "$Players players connect automatically on University; A hosts the lobby." }
+Write-Host 'Steam is not required. Click a game window to control that player with your controller.'
+Write-Host 'For two pads, use -TwoControllers (XInput slots 0 and 1). Use -Players 10 for the full lobby.'
+Write-Host "Logs: $logs"