[feature] Track skipped entries in InventoryPart

[paul-fresquet]

Summary

Add tracking of skipped entries to InventoryPart so that the system can report how many entries were excluded during inventory building and why.

Background

Currently, InventoryPart tracks:

• FileDescriptions — files included in inventory
• DirectoryDescriptions — directories included in inventory
• IsIncompleteDueToAccess — flag for access errors

There is no tracking of entries that were intentionally skipped (hidden files, noise files, symlinks, etc.).

Proposed Changes

Add to InventoryPart

public class InventoryPart
{
    // Existing properties...
    
    /// <summary>
    /// Entries that were skipped during inventory building.
    /// </summary>
    public List<SkippedEntry> SkippedEntries { get; } = new();
    
    /// <summary>
    /// Total count of skipped entries.
    /// </summary>
    public int SkippedCount => SkippedEntries.Count;
    
    /// <summary>
    /// Count of entries skipped for a specific reason.
    /// </summary>
    public int GetSkippedCountByReason(SkipReason reason) 
        => SkippedEntries.Count(e => e.Reason == reason);
}

Integration in InventoryBuilder

Add a helper method to record skipped entries:

private void RecordSkippedEntry(InventoryPart part, FileSystemInfo fsi, SkipReason reason, FileSystemEntryKind? kind = null)
{
    var skipped = new SkippedEntry
    {
        FullPath = fsi.FullName,
        RelativePath = BuildRelativePath(part, fsi),
        Name = fsi.Name,
        Reason = reason,
        DetectedKind = kind
    };
    part.SkippedEntries.Add(skipped);
}

Update Skip Points

Modify all skip points in InventoryBuilder to call RecordSkippedEntry:

• ShouldIgnoreHiddenFile() → SkipReason.Hidden
• ShouldIgnoreHiddenDirectory() → SkipReason.Hidden
• ShouldIgnoreSystemFile() → SkipReason.NoiseFile or SkipReason.SystemAttribute
• IsReparsePoint() → SkipReason.Symlink
• POSIX special file detection → SkipReason.SpecialPosixFile
• IsOffline() / IsRecallOnDataAccess() → SkipReason.Offline
• Access exceptions → SkipReason.Inaccessible

Acceptance Criteria

• Add SkippedEntries list to InventoryPart
• Add SkippedCount property
• Add GetSkippedCountByReason() method
• Create RecordSkippedEntry() helper in InventoryBuilder
• Update all skip points to record entries
• Integration tests verifying skipped entries are tracked
• Verify no performance regression with large directories

Technical Notes

• SkippedEntries is NOT serialized to inventory files (runtime only)
• Consider memory impact for directories with many excluded files
• May want to add a cap or sampling for extreme cases (future enhancement)

Dependencies

• Requires: SkippedEntry model and SkipReason enum (issue #X)

Priority

Standard — Foundation for UI reporting of skipped entries.