Generalize mod APIs, improve multiplayer and optimize mod rendering

Add generalized engine access and challenge mods, repair SKATE turn handling, and improve collision prediction and physics transitions. Reduce mod snapshot and material update overhead, preserve authored GLB materials with lighting and shadows, and improve CPU profiling.

scripts/Launch.ps1

@@ -40,15 +40,6 @@ Re-point assets to a valid installation, for example:
     $argumentList = '--assets "' + $assetsPath + '"'
     if (-not $Map -and $env:SKATE_TRACE_MAP) { $Map = $env:SKATE_TRACE_MAP }
     if (-not $TraceFile -and $env:SKATE_TRACE_FILE) { $TraceFile = $env:SKATE_TRACE_FILE }
-    if (-not $Map -and $Trace) {
-        $installRoot = Split-Path (Resolve-Path -LiteralPath $assetsPath).Path -Parent
-        foreach ($candidate in @(
-            (Join-Path $installRoot 'maps\DownTown.skate'),
-            (Join-Path $assetsPath 'private\native-backdrops\DownTown.skate')
-        )) {
-            if (Test-Path -LiteralPath $candidate) { $Map = $candidate; break }
-        }
-    }
     if ($Map) {
         $mapPath = (Resolve-Path -LiteralPath $Map).Path
         if ([System.IO.Path]::GetExtension($mapPath) -ine '.skate') { throw "Not a .skate map file: $mapPath" }
@@ -62,21 +53,14 @@ Re-point assets to a valid installation, for example:
             Join-Path $ProjectRoot 'trace-downtown-lag.json'
         }
         if (Test-Path -LiteralPath $tracePath) { Remove-Item -LiteralPath $tracePath -Force }
-        $argumentList += ' --trace "' + $tracePath + '" --trace-wait --trace-gpu'
+        $argumentList += ' --trace "' + $tracePath + '" --trace-wait --trace-seconds 10'
         Write-Host "Trace: $tracePath"
-        Write-Host 'F9 = start recording at lag spot, F10 = stop and export (open in https://ui.perfetto.dev)'
+        Write-Host 'F9 starts a 10-second CPU capture; export stops automatically. Open the JSON in Perfetto.'
     }
     # Dev packages live in repo mods/; the exe otherwise only looks beside bin/.
     $env:SKATE3_MODS = Join-Path $ProjectRoot 'mods'
     New-Item -ItemType Directory -Path $env:SKATE3_MODS -Force | Out-Null
     Write-Host "Mods: $env:SKATE3_MODS"
-    if ($Trace) {
-        # Use cmd start so the game gets a real window; PS Start-Process argument quoting is flaky.
-        $cmd = 'start "Skate3 Rust" /D "' + $ProjectRoot + '" "' + $executable + '" ' + $argumentList
-        Start-Process -FilePath 'cmd.exe' -ArgumentList '/c', $cmd -WorkingDirectory $ProjectRoot
-        Write-Host 'Game launched in its own window. Close it when you are done.'
-        return
-    }
     $game = Start-Process -FilePath $executable -WorkingDirectory $ProjectRoot `
         -ArgumentList $argumentList -NoNewWindow -Wait -PassThru `
         -RedirectStandardOutput $log -RedirectStandardError $errorLog