feat(08-04): add simplified export overloads to CsvExportService

- Add BuildCsv(IReadOnlyList<SimplifiedPermissionEntry>) overload with SimplifiedLabels and RiskLevel columns
- Add WriteAsync overload for simplified entries
- Original PermissionEntry methods unchanged

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

SharepointToolbox/Services/Export/CsvExportService.cs

@@ -58,6 +58,60 @@ public class CsvExportService
         await File.WriteAllTextAsync(filePath, csv, new UTF8Encoding(encoderShouldEmitUTF8Identifier: true), ct);
     }
 
+    /// <summary>
+    /// Header for simplified CSV export — includes "SimplifiedLabels" and "RiskLevel" columns.
+    /// </summary>
+    private const string SimplifiedHeader =
+        "\"Object\",\"Title\",\"URL\",\"HasUniquePermissions\",\"Users\",\"UserLogins\",\"Type\",\"Permissions\",\"SimplifiedLabels\",\"RiskLevel\",\"GrantedThrough\"";
+
+    /// <summary>
+    /// Builds a CSV string from simplified permission entries.
+    /// Includes SimplifiedLabels and RiskLevel columns after raw Permissions.
+    /// Uses the same merge logic as the standard BuildCsv.
+    /// </summary>
+    public string BuildCsv(IReadOnlyList<SimplifiedPermissionEntry> entries)
+    {
+        var sb = new StringBuilder();
+        sb.AppendLine(SimplifiedHeader);
+
+        var merged = entries
+            .GroupBy(e => (e.Users, e.PermissionLevels, e.GrantedThrough))
+            .Select(g => new
+            {
+                ObjectType     = g.First().ObjectType,
+                Title          = string.Join(" | ", g.Select(e => e.Title).Distinct()),
+                Url            = string.Join(" | ", g.Select(e => e.Url).Distinct()),
+                HasUnique      = g.First().HasUniquePermissions,
+                Users          = g.Key.Users,
+                UserLogins     = g.First().UserLogins,
+                PrincipalType  = g.First().PrincipalType,
+                Permissions    = g.Key.PermissionLevels,
+                SimplifiedLabels = g.First().SimplifiedLabels,
+                RiskLevel      = g.First().RiskLevel.ToString(),
+                GrantedThrough = g.Key.GrantedThrough
+            });
+
+        foreach (var row in merged)
+            sb.AppendLine(string.Join(",", new[]
+            {
+                Csv(row.ObjectType), Csv(row.Title), Csv(row.Url),
+                Csv(row.HasUnique.ToString()), Csv(row.Users), Csv(row.UserLogins),
+                Csv(row.PrincipalType), Csv(row.Permissions), Csv(row.SimplifiedLabels),
+                Csv(row.RiskLevel), Csv(row.GrantedThrough)
+            }));
+
+        return sb.ToString();
+    }
+
+    /// <summary>
+    /// Writes simplified CSV to the specified file path.
+    /// </summary>
+    public async Task WriteAsync(IReadOnlyList<SimplifiedPermissionEntry> entries, string filePath, CancellationToken ct)
+    {
+        var csv = BuildCsv(entries);
+        await File.WriteAllTextAsync(filePath, csv, new UTF8Encoding(encoderShouldEmitUTF8Identifier: true), ct);
+    }
+
     /// <summary>RFC 4180 CSV field escaping: wrap in double quotes, double internal quotes.</summary>
     private static string Csv(string value)
     {