Build Windows Source SDK dependencies before HL2MP DLLs

ddiff --git a/.github/workflows/windows-source-sdk-dlls.yml b/.github/workflows/windows-source-sdk-dlls.yml
iindex fd3971b..3726251 100644
---- a/.github/workflows/windows-source-sdk-dlls.yml
++++ b/.github/workflows/windows-source-sdk-dlls.yml
@@@ -46,6 +46,11 @@ jobs:
        - name: Setup MSBuild
          uses: microsoft/setup-msbuild@v2
  
++      - name: Setup Python
++        uses: actions/setup-python@v5
++        with:
++          python-version: "3.x"
++
        - name: Show toolchain and tree
          run: |
            $ErrorActionPreference = 'Continue'
ddiff --git a/tools/build-sdk-windows.ps1 b/tools/build-sdk-windows.ps1
iindex d162317..ad91425 100644
---- a/tools/build-sdk-windows.ps1
++++ b/tools/build-sdk-windows.ps1
@@@ -17,6 +17,31 @@ function Require($p, $msg) {
    if (!(Test-Path $p)) { throw "$msg`nMissing: $p" }
  }
  
++function Ensure-PythonOnPath {
++  $pyCmd = Get-Command python.exe -ErrorAction SilentlyContinue
++  if (-not $pyCmd) { $pyCmd = Get-Command python -ErrorAction SilentlyContinue }
++  if ($pyCmd) {
++    Say "python=$($pyCmd.Source)"
++    try { & $pyCmd.Source --version 2>&1 | Tee-Object -FilePath (Join-Path $LogDir "python-version.txt") | Out-Null } catch {}
++    return
++  }
++
++  $pyLauncher = Get-Command py.exe -ErrorAction SilentlyContinue
++  if ($pyLauncher) {
++    $shimDir = Join-Path $Root "_tools/python-shim"
++    New-Item -ItemType Directory -Force -Path $shimDir | Out-Null
++    $shim = Join-Path $shimDir "python.bat"
++    "@echo off`r`npy -3 %*`r`n" | Set-Content -Encoding ascii $shim
++    $env:PATH = "$shimDir;$env:PATH"
++    Say "python shim=$shim"
++    & python --version 2>&1 | Tee-Object -FilePath (Join-Path $LogDir "python-version.txt") | Out-Null
++    return
++  }
++
++  throw "python was not found on PATH and py.exe was not found. Add actions/setup-python before the build step."
++}
++
++
  function Find-VcVars64 {
    $candidates = @(
      "${env:ProgramFiles}\Microsoft Visual Studio\2022\Enterprise\VC\Auxiliary\Build\vcvars64.bat",
@@@ -53,6 +78,8 @@ Say "cl.exe already available"
  where.exe cl | Out-File (Join-Path $LogDir "where-cl.txt")
  where.exe msbuild | Out-File (Join-Path $LogDir "where-msbuild.txt")
  where.exe lib | Out-File (Join-Path $LogDir "where-lib.txt")
++Ensure-PythonOnPath
++
  
  # Apply OpenVibe source files using Git Bash when available. Skip Linux QuickJS build on Windows.
  $bash = (Get-Command bash -ErrorAction SilentlyContinue)
@@@ -197,6 +224,67 @@ function Invoke-MSBuildProject([System.IO.FileInfo]$proj, [string]$label) {
    return $false
  }
  
++
++function Find-ProjectByPattern([string]$pattern) {
++  return @(Get-ChildItem -Path $Src -Recurse -File -Filter $pattern -ErrorAction SilentlyContinue |
++    Sort-Object @{ Expression = { if ($_.FullName -match "\\(mathlib|tier1|raytrace|vgui2|fgdlib)\\") { 0 } else { 1 } } }, FullName)
++}
++
++function Copy-LibIfNeeded([string]$libName, [string]$destDir) {
++  New-Item -ItemType Directory -Force -Path $destDir | Out-Null
++  $dest = Join-Path $destDir $libName
++  if (Test-Path $dest) { return }
++  $found = Get-ChildItem -Path $Sdk -Recurse -File -Filter $libName -ErrorAction SilentlyContinue |
++    Where-Object { $_.FullName -notmatch "artifacts|windows-build-debug|_deps" } |
++    Sort-Object LastWriteTime -Descending |
++    Select-Object -First 1
++  if ($found) {
++    Say "copying fallback lib $($found.FullName) -> $dest"
++    Copy-Item $found.FullName $dest -Force
++  }
++}
++
++function Build-SourceSdkDependencyProjects {
++  Say "building Source SDK dependency libraries before HL2MP client/server"
++
++  $patterns = @(
++    "tier1*_win64.vcxproj",
++    "mathlib*_win64.vcxproj",
++    "raytrace*_win64.vcxproj",
++    "vgui_controls*_win64.vcxproj",
++    "matsys_controls*_win64.vcxproj",
++    "fgdlib*_win64.vcxproj"
++  )
++
++  $projects = @()
++  foreach ($pat in $patterns) {
++    $projects += Find-ProjectByPattern $pat
++  }
++  $projects = @($projects | Sort-Object FullName -Unique)
++
++  "=== dependency projects ===" | Out-File (Join-Path $LogDir "dependency-projects.txt")
++  $projects | Select-Object FullName,Length,LastWriteTime | Format-List | Out-File (Join-Path $LogDir "dependency-projects.txt") -Append
++
++  foreach ($dep in $projects) {
++    $label = "dep-$($dep.BaseName -replace '[^A-Za-z0-9]+','_')"
++    [void](Invoke-MSBuildProject $dep $label)
++  }
++
++  $publicX64 = Join-Path $Src "lib/public/x64"
++  Copy-LibIfNeeded "mathlib.lib" $publicX64
++  Copy-LibIfNeeded "tier1.lib" $publicX64
++  Copy-LibIfNeeded "raytrace.lib" $publicX64
++  Copy-LibIfNeeded "vgui_controls.lib" $publicX64
++  Copy-LibIfNeeded "matsys_controls.lib" $publicX64
++
++  "=== public x64 libs after deps ===" | Out-File (Join-Path $LogDir "public-x64-libs-after-deps.txt")
++  if (Test-Path $publicX64) {
++    Get-ChildItem -Path $publicX64 -File -ErrorAction SilentlyContinue |
++      Select-Object FullName,Length,LastWriteTime |
++      Format-List | Out-File (Join-Path $LogDir "public-x64-libs-after-deps.txt") -Append
++  }
++}
++
  # Generate projects if no relevant vcxproj files exist yet.
  $clientProjects = @(Get-ChildItem -Path $Src -Recurse -File -Filter "*client*hl2mp*.vcxproj" -ErrorAction SilentlyContinue)
  $serverProjects = @(Get-ChildItem -Path $Src -Recurse -File -Filter "*server*hl2mp*.vcxproj" -ErrorAction SilentlyContinue)
@@@ -239,6 +327,8 @@ $serverProject = $serverProjects |
                FullName |
    Select-Object -First 1
  
++Build-SourceSdkDependencyProjects
++
  $beforeBuild = Get-Date
  
  if (-not (Invoke-MSBuildProject $clientProject "client")) {