Generate Win32 placeholder libs for missing SDK inputs

ddiff --git a/docs/WINDOWS_WIN32_PLACEHOLDER_LIB_RESOLVER.md b/docs/WINDOWS_WIN32_PLACEHOLDER_LIB_RESOLVER.md
nnew file mode 100644
iindex 0000000..93e5f40
---- /dev/null
++++ b/docs/WINDOWS_WIN32_PLACEHOLDER_LIB_RESOLVER.md
@@@ -0,0 +1,11 @@
++# Windows Win32 placeholder lib resolver
++
++The Proton-compatible build targets 32-bit Source SDK Base 2013 Multiplayer. Current Valve VPC output may reference old Win32 `.lib` inputs that are not present in the public GitHub checkout.
++
++The Windows build now performs three passes before linking HL2MP DLLs:
++
++1. Build/copy real Source SDK dependency projects where possible.
++2. Dynamically read `<AdditionalDependencies>` from selected client/server vcxproj files and copy any real matching libs found in the SDK tree.
++3. For any remaining missing non-system `.lib` inputs, generate a tiny x86 placeholder archive with MSVC `cl.exe` + `lib.exe`.
++
++This converts opaque one-at-a-time `LNK1181: cannot open input file` failures into a real linker result. If a missing library actually provides required symbols, the build will still fail with unresolved externals, which points at the real missing implementation instead of just the missing file.
ddiff --git a/tools/build-sdk-windows.ps1 b/tools/build-sdk-windows.ps1
iindex 0ae198e..c0cfffe 100644
---- a/tools/build-sdk-windows.ps1
++++ b/tools/build-sdk-windows.ps1
@@@ -947,6 +947,122 @@ function Ensure-OpenVibeWin32ImportCompatibilityLibs {
    }
  }
  
++
++# OPENVIBE_WIN32_GENERATE_ALL_MISSING_PLACEHOLDER_LIBS
++# Last-resort compatibility layer for Proton Win32 DLL builds.
++# VPC on current Windows runners can emit HL2MP projects that reference old SDK import/static
++# libraries that are not shipped in ValveSoftware/source-sdk-2013's Win32 public lib folder.
++# We first build/copy real libs. For remaining missing .lib inputs, create tiny x86 archives so
++# the linker can continue. If the DLL actually uses a missing symbol, the link will still fail
++# later with an unresolved external, which is more useful than one-at-a-time LNK1181 missing-file
++# failures.
++function Get-OpenVibeAdditionalDependencyLibNames {
++  param([System.IO.FileInfo[]]$Projects)
++
++  $systemLibs = [System.Collections.Generic.HashSet[string]]::new([System.StringComparer]::OrdinalIgnoreCase)
++  foreach ($lib in @(
++    'kernel32.lib','user32.lib','gdi32.lib','winspool.lib','comdlg32.lib',
++    'advapi32.lib','shell32.lib','ole32.lib','oleaut32.lib','uuid.lib',
++    'odbc32.lib','odbccp32.lib','winmm.lib','ws2_32.lib','dbghelp.lib',
++    'psapi.lib','comctl32.lib','shlwapi.lib','imm32.lib','version.lib',
++    'Rpcrt4.lib','opengl32.lib','legacy_stdio_definitions.lib',
++    'libcmt.lib','libcmtd.lib','msvcrt.lib','msvcrtd.lib',
++    'libcpmt.lib','libcpmtd.lib','libc.lib','msvcprt.lib','msvcprtd.lib',
++    'setupapi.lib','dxguid.lib','dinput8.lib','d3d9.lib','d3dx9.lib',
++    'Strmiids.lib','delayimp.lib','ntdll.lib','wldap32.lib','crypt32.lib'
++  )) { [void]$systemLibs.Add($lib) }
++
++  $libs = [System.Collections.Generic.SortedSet[string]]::new([System.StringComparer]::OrdinalIgnoreCase)
++  foreach ($proj in $Projects) {
++    if (-not $proj -or !(Test-Path $proj.FullName)) { continue }
++    $text = Get-Content -Raw $proj.FullName
++    $matches = [regex]::Matches($text, '<AdditionalDependencies>(.*?)</AdditionalDependencies>', [System.Text.RegularExpressions.RegexOptions]::Singleline)
++    foreach ($m in $matches) {
++      foreach ($tokRaw in ($m.Groups[1].Value -split ';')) {
++        $tok = ([string]$tokRaw).Trim()
++        if ($tok -eq '' -or $tok -match '^%\(' -or $tok -match '^\$\(') { continue }
++        $lm = [regex]::Match($tok, '([^\\/;<>]+\.lib)\s*$', [System.Text.RegularExpressions.RegexOptions]::IgnoreCase)
++        if (-not $lm.Success) { continue }
++        $leaf = $lm.Groups[1].Value
++        if ($leaf -and -not $systemLibs.Contains($leaf)) { [void]$libs.Add($leaf) }
++      }
++    }
++  }
++  return @($libs)
++}
++
++function New-OpenVibeX86PlaceholderLib {
++  param(
++    [string]$LibName,
++    [string]$DestPath,
++    [string]$StubDir,
++    [string]$LogPath
++  )
++
++  New-Item -ItemType Directory -Force -Path $StubDir | Out-Null
++  $base = [System.IO.Path]::GetFileNameWithoutExtension($LibName)
++  $safe = ($base -replace '[^A-Za-z0-9_]+','_')
++  if (-not $safe) { $safe = 'lib' }
++  $c = Join-Path $StubDir "$safe.c"
++  $obj = Join-Path $StubDir "$safe.obj"
++  $symbol = "openvibe_placeholder_${safe}"
++
++  "void $symbol(void) {}" | Set-Content -Encoding ascii -Path $c
++  "[placeholder] creating $LibName at $DestPath" | Out-File $LogPath -Append
++  & cl.exe /nologo /TC /c $c "/Fo$obj" 2>&1 | Tee-Object -FilePath $LogPath -Append | Out-Host
++  if ($LASTEXITCODE -ne 0 -or !(Test-Path $obj)) {
++    throw "cl.exe failed while creating placeholder object for $LibName. Check win32-placeholder-libs.txt."
++  }
++
++  & lib.exe /nologo /machine:X86 "/out:$DestPath" $obj 2>&1 | Tee-Object -FilePath $LogPath -Append | Out-Host
++  if ($LASTEXITCODE -ne 0 -or !(Test-Path $DestPath)) {
++    throw "lib.exe failed while creating placeholder library $DestPath. Check win32-placeholder-libs.txt."
++  }
++}
++
++function Ensure-OpenVibeWin32PlaceholderLibsForRemainingDeps {
++  param(
++    [System.IO.FileInfo[]]$Projects,
++    [string]$PublicLibDir
++  )
++
++  if ($script:OpenVibeTargetArch -ne 'x86') { return }
++
++  $log = Join-Path $LogDir 'win32-placeholder-libs.txt'
++  "=== Ensure-OpenVibeWin32PlaceholderLibsForRemainingDeps ===" | Out-File $log
++  "publicLibDir=$PublicLibDir" | Out-File $log -Append
++  "targetArch=$script:OpenVibeTargetArch" | Out-File $log -Append
++
++  New-Item -ItemType Directory -Force -Path $PublicLibDir | Out-Null
++  $stubDir = Join-Path $LogDir 'win32-placeholder-lib-objs'
++  $libs = @(Get-OpenVibeAdditionalDependencyLibNames -Projects $Projects)
++
++  "referenced non-system libs ($($libs.Count)):" | Out-File $log -Append
++  $libs | ForEach-Object { "  $_" | Out-File $log -Append }
++
++  $created = New-Object System.Collections.Generic.List[string]
++  foreach ($lib in $libs) {
++    # Previous conversion should have rewritten steam_api64.lib to steam_api.lib, but guard anyway.
++    if ($lib -ieq 'steam_api64.lib') { $lib = 'steam_api.lib' }
++    $dest = Join-Path $PublicLibDir $lib
++    if (Test-Path $dest) {
++      $item = Get-Item $dest
++      "[present] $lib length=$($item.Length)" | Out-File $log -Append
++      continue
++    }
++
++    New-OpenVibeX86PlaceholderLib -LibName $lib -DestPath $dest -StubDir $stubDir -LogPath $log
++    [void]$created.Add($lib)
++  }
++
++  if ($created.Count -gt 0) {
++    Say "created x86 placeholder lib(s): $($created -join ', ')"
++  } else {
++    Say "no Win32 placeholder libs were needed"
++  }
++}
++
++
  # 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)
@@@ -1023,6 +1139,9 @@ Build-SourceSdkDependencyProjects
  # OPENVIBE_RESOLVE_WIN32_PUBLIC_LIB_DEPS_CALL
  $resolvePublicLibDir = if ($script:OpenVibeTargetArch -eq "x86") { Join-Path $Src "lib/public" } else { Join-Path $Src "lib/public/x64" }
  Resolve-OpenVibeWin32PublicLibDependencies -Projects @($clientProject, $serverProject) -PublicLibDir $resolvePublicLibDir
++# OPENVIBE_WIN32_GENERATE_ALL_MISSING_PLACEHOLDER_LIBS_CALL
++Ensure-OpenVibeWin32PlaceholderLibsForRemainingDeps -Projects @($clientProject, $serverProject) -PublicLibDir $resolvePublicLibDir
++
  
  # OPENVIBE_WIN32_IMPORT_COMPAT_LIB_STUBS_CALL
  Ensure-OpenVibeWin32ImportCompatibilityLibs