Fix pruned FFmpeg release inputs

native/age_movie_ffmpeg/bootstrap-win64.ps1

@@ -10,11 +10,24 @@ if ([string]::IsNullOrWhiteSpace($Destination)) {
 $manifest = Get-Content -LiteralPath (Join-Path $PSScriptRoot 'dependency-win64.json') -Raw | ConvertFrom-Json
 $downloadDir = Join-Path $repoRoot 'build\downloads'
 $archivePath = Join-Path $downloadDir $manifest.archive
+$partialArchivePath = "$archivePath.part"
 $extractRoot = Join-Path $Destination ([IO.Path]::GetFileNameWithoutExtension($manifest.archive))
 New-Item -ItemType Directory -Force -Path $downloadDir | Out-Null
 
 if (-not (Test-Path -LiteralPath $archivePath)) {
-    Invoke-WebRequest -Uri $manifest.url -OutFile $archivePath
+    try {
+        Invoke-WebRequest -Uri $manifest.url -OutFile $partialArchivePath
+        Move-Item -LiteralPath $partialArchivePath -Destination $archivePath
+    }
+    finally {
+        if (Test-Path -LiteralPath $partialArchivePath) {
+            Remove-Item -LiteralPath $partialArchivePath -Force
+        }
+    }
+}
+$actualSize = (Get-Item -LiteralPath $archivePath).Length
+if ($actualSize -ne $manifest.size) {
+    throw "FFmpeg archive size mismatch: expected $($manifest.size), got $actualSize"
 }
 $actualHash = (Get-FileHash -Algorithm SHA256 -LiteralPath $archivePath).Hash.ToLowerInvariant()
 if ($actualHash -ne $manifest.sha256) {
@@ -28,7 +41,7 @@ if (-not (Test-Path -LiteralPath (Join-Path $sdkRoot 'include\libavformat\avform
     throw "Pinned FFmpeg SDK was not found at $sdkRoot"
 }
 $reported = & (Join-Path $sdkRoot 'bin\ffmpeg.exe') -version | Select-Object -First 1
-$expectedVersion = $manifest.ffmpeg_version -replace '-20260721$', ''
+$expectedVersion = $manifest.ffmpeg_version -replace '-\d{8}$', ''
 if ($reported -notlike "*$expectedVersion*" ) {
     throw "Unexpected FFmpeg build: $reported"
 }