feat: migrate legacy playout workflow and scenes

scripts/Test-LegacySceneBaseline.ps1

@@ -0,0 +1,52 @@
+[CmdletBinding()]
+param(
+    [string] $LegacyProjectRoot,
+    [string] $ManifestPath
+)
+
+$ErrorActionPreference = 'Stop'
+if ([string]::IsNullOrWhiteSpace($LegacyProjectRoot)) {
+    $LegacyProjectRoot = Join-Path $PSScriptRoot '..\..\MBN_STOCK_N\MBN_STOCK_N'
+}
+if ([string]::IsNullOrWhiteSpace($ManifestPath)) {
+    $ManifestPath = Join-Path $PSScriptRoot '..\docs\legacy-scene-source-hashes.json'
+}
+$legacyRoot = [IO.Path]::GetFullPath($LegacyProjectRoot)
+$manifestFile = [IO.Path]::GetFullPath($ManifestPath)
+
+if (-not (Test-Path -LiteralPath $legacyRoot -PathType Container)) {
+    throw 'The read-only legacy project root was not found.'
+}
+
+if (-not (Test-Path -LiteralPath $manifestFile -PathType Leaf)) {
+    throw 'The legacy scene hash manifest was not found.'
+}
+
+$manifest = Get-Content -LiteralPath $manifestFile -Raw -Encoding UTF8 | ConvertFrom-Json
+if ($manifest.schemaVersion -ne 1 -or
+    $manifest.algorithm -ne 'SHA-256' -or
+    $manifest.builders.Count -ne 35) {
+    throw 'The legacy scene hash manifest is invalid.'
+}
+
+$seen = [Collections.Generic.HashSet[string]]::new([StringComparer]::Ordinal)
+foreach ($entry in $manifest.builders) {
+    if (-not $seen.Add([string] $entry.builder)) {
+        throw 'The legacy scene hash manifest contains a duplicate builder.'
+    }
+
+    $relativePath = ([string] $entry.sourceFile).Replace('/', [IO.Path]::DirectorySeparatorChar)
+    $sourceFile = [IO.Path]::GetFullPath((Join-Path $legacyRoot $relativePath))
+    $rootPrefix = $legacyRoot.TrimEnd([IO.Path]::DirectorySeparatorChar) + [IO.Path]::DirectorySeparatorChar
+    if (-not $sourceFile.StartsWith($rootPrefix, [StringComparison]::OrdinalIgnoreCase) -or
+        -not (Test-Path -LiteralPath $sourceFile -PathType Leaf)) {
+        throw "Legacy source is missing for $($entry.builder)."
+    }
+
+    $actual = (Get-FileHash -LiteralPath $sourceFile -Algorithm SHA256).Hash
+    if (-not $actual.Equals([string] $entry.sha256, [StringComparison]::OrdinalIgnoreCase)) {
+        throw "Legacy source baseline changed for $($entry.builder)."
+    }
+}
+
+Write-Output "LEGACY_SCENE_BASELINE: PASS ($($seen.Count)/35)"