Extract file metadata for DiscUtils-based disc image formats

[Copilot]

• Add FileAttributes property to FileEntryMetadata for Windows file attributes (NTFS/FAT/WIM)
• Add SecurityDescriptorSddl property to FileEntryMetadata for NTFS security descriptor in SDDL format
• Update DiscCommon.TryGetFileMetadata() to handle IDosFileSystem (file attributes) and IWindowsFileSystem (security descriptors)
• Update DiscCommon.CollectMetadata() to recognize Windows file systems
• Add tests for VHDX (NTFS) metadata extraction (FileAttributes + SecurityDescriptorSddl)
• Update MetadataDefaults_AreNull test for new properties
• All 598 tests + 35 CLI tests pass
• Restore nuget.config
• Code review passed
• Security review (manual: no vulnerabilities found - all changes read metadata from existing DiscUtils APIs with proper exception handling)

Original prompt

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This section details on the original issue you should resolve

<issue_title>Extract File MetaData for DiscUtils based Disc Image formats</issue_title>
<issue_description>Extending work done for #82, in #196.

We should expand the file meta data collection to the Disc image formats we support to keep feature parity, but this is broken out into a separate issue because its a bit more complex of an implementation.

It seems like to accomplish, we need to on each file extracted in DiscCommon check for each potential file system format. For example, if the underlying file system is NTFS, we would need to check with something like https://github.com/LTRData/DiscUtils/blob/5e02b5e22d0bfd16ee3c99ee4e6ae72591589d1c/Library/DiscUtils.Ntfs/NtfsFileSystem.cs#L1292. </issue_description>

Comments on the Issue (you are @copilot in this section)

• Fixes Extract File MetaData for DiscUtils based Disc Image formats #197

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[Copilot]

Pull request overview

Adds DiscUtils-backed filesystem metadata extraction so disc image formats (ISO/UDF/VHDX/WIM) can populate FileEntry.Metadata similarly to existing archive extractors, including Windows-specific NTFS/FAT metadata.

Changes:

• Extend FileEntryMetadata with Windows FileAttributes and NTFS SecurityDescriptorSddl.
• Add DiscCommon.TryGetFileMetadata() / CollectMetadata() and wire metadata into DiscUtils-based extractors.
• Add/expand tests and fixtures for ISO RockRidge Unix metadata and VHDX (NTFS) Windows metadata.

Reviewed changes

Copilot reviewed 9 out of 10 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
nuget.config	Normalizes XML header/format (restored feed configuration).
RecursiveExtractor/FileEntryMetadata.cs	Adds Windows file attributes + SDDL fields to metadata model.
RecursiveExtractor/Extractors/DiscCommon.cs	Implements DiscUtils metadata extraction and pre-collection helper.
RecursiveExtractor/Extractors/WimExtractor.cs	Sets metadata per extracted WIM entry via DiscCommon.
RecursiveExtractor/Extractors/IsoExtractor.cs	Pre-collects metadata while ISO FS is open and assigns to entries.
RecursiveExtractor/Extractors/UdfExtractor.cs	Pre-collects metadata while UDF FS is open and assigns to entries.
RecursiveExtractor.Tests/RecursiveExtractor.Tests.csproj	Includes new RockRidge ISO test fixture in outputs.
RecursiveExtractor.Tests/ExtractorTests/FileMetadataTests.cs	Adds coverage for ISO (with/without RockRidge) and VHDX NTFS metadata.
RecursiveExtractor.Tests/ExtractorTests/ExpectedNumFilesTests.cs	Adds expected file counts for the new RockRidge ISO fixture.

[Copilot]

The XML doc comment lists examples of IUnixFileSystem implementations (Ext/Xfs/Btrfs/HfsPlus) but this helper is also used for ISO via DiscUtils.Iso9660.CDReader, which implements IUnixFileSystem only when RockRidge metadata is present. Consider updating the comment to include CDReader/ISO and note the RockRidge requirement (or clarify that the list is non-exhaustive) to avoid misleading future readers.

Suggested change

	/// For file systems implementing <see cref="IUnixFileSystem"/> (Ext, Xfs, Btrfs, HfsPlus),
	/// returns permissions, UID, and GID.
	/// For file systems implementing <see cref="IDosFileSystem"/> (NTFS, FAT, WIM),
	/// returns Windows file attributes.
	/// For file systems implementing <see cref="IWindowsFileSystem"/> (NTFS, WIM),
	/// For file systems implementing <see cref="IUnixFileSystem"/> (such as Ext, Xfs, Btrfs, HfsPlus,
	/// and ISO images via <c>DiscUtils.Iso9660.CDReader</c> when RockRidge extensions are present),
	/// returns permissions, UID, and GID.
	/// For file systems implementing <see cref="IDosFileSystem"/> (such as NTFS, FAT, WIM),
	/// returns Windows file attributes.
	/// For file systems implementing <see cref="IWindowsFileSystem"/> (such as NTFS, WIM),