test: add isolated cross-version application compatibility harness

scripts/e2e/test-opcua-sdk-compatibility.ps1

@@ -0,0 +1,22 @@
+#Requires -Version 7.0
+<#
+.SYNOPSIS
+Runs the production application SDK compatibility matrix in isolated processes.
+.DESCRIPTION
+Uses exact baseline host/client publish artifacts and builds the candidate from a
+separate checkout. Both SDK versions remain in separate processes. Evidence,
+artifact SHA-256 hashes, negotiated policies and individual results are retained.
+The output directory must not exist. No fleet endpoint or store is used.
+#>
+[CmdletBinding()]
+param(
+    [Parameter(Mandatory)][string]$BaselineRoot,
+    [Parameter(Mandatory)][string]$BaselineArtifacts,
+    [Parameter(Mandatory)][string]$CandidateRoot,
+    [Parameter(Mandatory)][string]$OutputDirectory,
+    [string]$ContainerImage = 'mcr.microsoft.com/dotnet/sdk:10.0.103-noble'
+)
+$ErrorActionPreference = 'Stop'
+$runner = Join-Path $PSScriptRoot '../validation/opcua-sdk-compatibility/run.py'
+& python3 $runner --baseline-root $BaselineRoot --baseline-artifacts $BaselineArtifacts --candidate-root $CandidateRoot --output $OutputDirectory --container-image $ContainerImage
+exit $LASTEXITCODE