feat: add msglib readonly sidecar

scripts/build-msglib-sidecar.ps1

@@ -0,0 +1,53 @@
+param(
+    [string]$OutputDir = "runs/msglib-sidecar",
+    [string]$Configuration = "Release"
+)
+
+$ErrorActionPreference = "Stop"
+
+$repo = Resolve-Path -LiteralPath (Join-Path $PSScriptRoot "..")
+$sourceDir = Join-Path $repo "native/MsgLibReadSidecar"
+$outDirPath = Join-Path $repo $OutputDir
+$outExe = Join-Path $outDirPath "MsgLibReadSidecar.exe"
+
+if (-not (Test-Path -LiteralPath $sourceDir)) {
+    throw "source directory not found: $sourceDir"
+}
+
+$csc = "$env:WINDIR\Microsoft.NET\Framework\v4.0.30319\csc.exe"
+if (-not (Test-Path -LiteralPath $csc)) {
+    throw "32-bit .NET Framework csc.exe v4.0.30319 not found"
+}
+
+New-Item -ItemType Directory -Force -Path $outDirPath | Out-Null
+
+$sources = Get-ChildItem -LiteralPath $sourceDir -Filter '*.cs' | Sort-Object Name | ForEach-Object { $_.FullName }
+if (-not $sources) {
+    throw "no C# sources found in $sourceDir"
+}
+
+& $csc `
+    /nologo `
+    /target:exe `
+    /platform:x86 `
+    /optimize+ `
+    /warn:0 `
+    /out:$outExe `
+    /reference:System.dll `
+    /reference:System.Core.dll `
+    /reference:System.Data.dll `
+    /reference:System.Web.Extensions.dll `
+    $sources
+
+if ($LASTEXITCODE -ne 0) {
+    throw "MsgLib sidecar compilation failed with exit code $LASTEXITCODE"
+}
+
+[ordered]@{
+    ok = $true
+    configuration = $Configuration
+    platform = "x86"
+    csc = $csc
+    source_dir = $sourceDir
+    output = $outExe
+} | ConvertTo-Json -Depth 4 -Compress