feat(03-01): create Phase 3 export stubs and test scaffolds

- Add StorageCsvExportService, StorageHtmlExportService stub (Plan 03-03)
- Add SearchCsvExportService, SearchHtmlExportService stub (Plan 03-05)
- Add DuplicatesHtmlExportService stub (Plan 03-05)
- Add StorageServiceTests, SearchServiceTests, DuplicatesServiceTests scaffolds
- Add export test scaffolds for all 4 Phase 3 export services
- 7 pure-logic tests pass (VersionSizeBytes + MakeKey); 4 CSOM stubs skip

SharepointToolbox/Services/Export/DuplicatesHtmlExportService.cs

@@ -0,0 +1,14 @@
+using SharepointToolbox.Core.Models;
+
+namespace SharepointToolbox.Services.Export;
+
+public class DuplicatesHtmlExportService
+{
+    public string BuildHtml(IReadOnlyList<DuplicateGroup> groups) => string.Empty; // implemented in Plan 03-05
+
+    public async Task WriteAsync(IReadOnlyList<DuplicateGroup> groups, string filePath, CancellationToken ct)
+    {
+        var html = BuildHtml(groups);
+        await System.IO.File.WriteAllTextAsync(filePath, html, System.Text.Encoding.UTF8, ct);
+    }
+}

SharepointToolbox/Services/Export/SearchCsvExportService.cs

@@ -0,0 +1,14 @@
+using SharepointToolbox.Core.Models;
+
+namespace SharepointToolbox.Services.Export;
+
+public class SearchCsvExportService
+{
+    public string BuildCsv(IReadOnlyList<SearchResult> results) => string.Empty; // implemented in Plan 03-05
+
+    public async Task WriteAsync(IReadOnlyList<SearchResult> results, string filePath, CancellationToken ct)
+    {
+        var csv = BuildCsv(results);
+        await System.IO.File.WriteAllTextAsync(filePath, csv, new System.Text.UTF8Encoding(true), ct);
+    }
+}

SharepointToolbox/Services/Export/SearchHtmlExportService.cs

@@ -0,0 +1,14 @@
+using SharepointToolbox.Core.Models;
+
+namespace SharepointToolbox.Services.Export;
+
+public class SearchHtmlExportService
+{
+    public string BuildHtml(IReadOnlyList<SearchResult> results) => string.Empty; // implemented in Plan 03-05
+
+    public async Task WriteAsync(IReadOnlyList<SearchResult> results, string filePath, CancellationToken ct)
+    {
+        var html = BuildHtml(results);
+        await System.IO.File.WriteAllTextAsync(filePath, html, System.Text.Encoding.UTF8, ct);
+    }
+}

SharepointToolbox/Services/Export/StorageCsvExportService.cs

@@ -0,0 +1,14 @@
+using SharepointToolbox.Core.Models;
+
+namespace SharepointToolbox.Services.Export;
+
+public class StorageCsvExportService
+{
+    public string BuildCsv(IReadOnlyList<StorageNode> nodes) => string.Empty; // implemented in Plan 03-03
+
+    public async Task WriteAsync(IReadOnlyList<StorageNode> nodes, string filePath, CancellationToken ct)
+    {
+        var csv = BuildCsv(nodes);
+        await System.IO.File.WriteAllTextAsync(filePath, csv, new System.Text.UTF8Encoding(true), ct);
+    }
+}

SharepointToolbox/Services/Export/StorageHtmlExportService.cs

@@ -0,0 +1,14 @@
+using SharepointToolbox.Core.Models;
+
+namespace SharepointToolbox.Services.Export;
+
+public class StorageHtmlExportService
+{
+    public string BuildHtml(IReadOnlyList<StorageNode> nodes) => string.Empty; // implemented in Plan 03-03
+
+    public async Task WriteAsync(IReadOnlyList<StorageNode> nodes, string filePath, CancellationToken ct)
+    {
+        var html = BuildHtml(nodes);
+        await System.IO.File.WriteAllTextAsync(filePath, html, System.Text.Encoding.UTF8, ct);
+    }
+}