chore: import upstream snapshot with attribution

scripts/generate-integrity-tree.ps1

@@ -0,0 +1,58 @@
+#!/usr/bin/env pwsh
+<#
+.SYNOPSIS
+    Generates an IntegrityTree.json file containing SHA256 hashes of all files
+    in the specified directory. Used at build time; verified at runtime by
+    UniGetUI.Core.Tools.IntegrityTester.
+
+.PARAMETER Path
+    The directory to scan (typically the publish/output directory).
+
+.PARAMETER MinOutput
+    Suppress per-file progress output.
+#>
+
+[CmdletBinding()]
+param(
+    [Parameter(Mandatory, Position = 0)]
+    [string] $Path,
+
+    [switch] $MinOutput
+)
+
+$ErrorActionPreference = 'Stop'
+
+if (-not (Test-Path $Path -PathType Container)) {
+    throw "The directory '$Path' does not exist."
+}
+
+$Path = (Resolve-Path $Path).Path
+$OutputFileName = 'IntegrityTree.json'
+$ScriptName = [System.IO.Path]::GetFileName($PSCommandPath)
+
+$integrityData = [ordered]@{}
+
+Get-ChildItem $Path -Recurse -File | ForEach-Object {
+    $relativePath = $_.FullName.Substring($Path.Length).TrimStart('\', '/') -replace '\\', '/'
+
+    # Skip the output file itself
+    if ($relativePath -eq $OutputFileName) { return }
+
+    if (-not $MinOutput) {
+        Write-Host " - Computing SHA256 of $relativePath..."
+    }
+
+    $hash = (Get-FileHash $_.FullName -Algorithm SHA256).Hash.ToLower()
+    $integrityData[$relativePath] = $hash
+}
+
+# Sort keys for deterministic output
+$sorted = [ordered]@{}
+foreach ($key in ($integrityData.Keys | Sort-Object)) {
+    $sorted[$key] = $integrityData[$key]
+}
+
+$json = $sorted | ConvertTo-Json -Depth 1
+Set-Content (Join-Path $Path $OutputFileName) $json -Encoding utf8NoBOM -NoNewline
+
+Write-Host "Integrity tree was generated and saved to $Path/$OutputFileName"