Add validated Linux Godot export

tools/export-linux-x64.ps1

@@ -0,0 +1,68 @@
+param(
+    [Parameter(Mandatory = $true)]
+    [string]$GodotConsole
+)
+
+$ErrorActionPreference = 'Stop'
+$repoRoot = (Resolve-Path (Join-Path $PSScriptRoot '..')).Path
+$projectRoot = Join-Path $repoRoot 'godot'
+$godotConsolePath = (Resolve-Path -LiteralPath $GodotConsole).Path
+$outputDirectory = [System.IO.Path]::GetFullPath((Join-Path $repoRoot 'build\export\linux-x64'))
+$expectedOutputDirectory = [System.IO.Path]::GetFullPath((Join-Path $repoRoot 'build\export\linux-x64'))
+$executable = Join-Path $outputDirectory 'Himegari.x86_64'
+
+if (-not (Test-Path -LiteralPath $godotConsolePath -PathType Leaf)) {
+    throw "Godot console executable was not found: $godotConsolePath"
+}
+foreach ($required in @(
+    (Join-Path $projectRoot 'Himegari.sln'),
+    (Join-Path $projectRoot 'export_presets.cfg'),
+    (Join-Path $repoRoot 'build\native\linux-x64\libage_movie_ffmpeg.so')
+)) {
+    if (-not (Test-Path -LiteralPath $required -PathType Leaf)) {
+        throw "Linux export prerequisite was not found: $required"
+    }
+}
+
+if (-not $outputDirectory.Equals($expectedOutputDirectory, [System.StringComparison]::OrdinalIgnoreCase)) {
+    throw "Refusing to clean unexpected export directory: $outputDirectory"
+}
+if (Test-Path -LiteralPath $outputDirectory) {
+    Remove-Item -LiteralPath $outputDirectory -Recurse -Force
+}
+New-Item -ItemType Directory -Path $outputDirectory | Out-Null
+
+& $godotConsolePath --headless --quit-after 120 --path $projectRoot --export-release 'Linux x86_64' $executable
+if ($LASTEXITCODE -ne 0) {
+    throw "Godot Linux x64 export failed with exit code $LASTEXITCODE. Install the Godot 4.7 .NET export templates and retry."
+}
+
+$managedDirectory = Join-Path $outputDirectory 'data_Himegari_linuxbsd_x86_64'
+foreach ($required in @(
+    $executable,
+    (Join-Path $outputDirectory 'Himegari.pck'),
+    (Join-Path $managedDirectory 'Himegari.dll'),
+    (Join-Path $managedDirectory 'Age.Engine.dll'),
+    (Join-Path $managedDirectory 'libage_movie_ffmpeg.so'),
+    (Join-Path $managedDirectory 'libavformat.so.62'),
+    (Join-Path $managedDirectory 'libavcodec.so.62'),
+    (Join-Path $managedDirectory 'libavutil.so.60'),
+    (Join-Path $managedDirectory 'libswscale.so.9'),
+    (Join-Path $managedDirectory 'libswresample.so.6'),
+    (Join-Path $managedDirectory 'FFmpeg-LICENSE.txt')
+)) {
+    if (-not (Test-Path -LiteralPath $required -PathType Leaf)) {
+        throw "Linux export is incomplete; expected artifact was not found: $required"
+    }
+}
+foreach ($forbidden in @(
+    (Join-Path $managedDirectory 'Age.Engine.Text.Windows.dll'),
+    (Join-Path $managedDirectory 'age_movie_ffmpeg.dll'),
+    (Join-Path $managedDirectory 'avformat-62.dll')
+)) {
+    if (Test-Path -LiteralPath $forbidden) {
+        throw "Linux export contains a Windows-only artifact: $forbidden"
+    }
+}
+
+Write-Output "Linux x64 export: $outputDirectory"