Add Git overlay, operation tools, and virtualized preview so large folders stay responsive.

Co-authored-by: Cursor <cursoragent@cursor.com>

src/Explorer.App/DocumentationLoader.cs

@@ -0,0 +1,55 @@
+using System.IO;
+using System.Reflection;
+
+namespace Explorer.App;
+
+public static class DocumentationLoader
+{
+    public const string EmbeddedName = "Explorer.Documentation.md";
+    public const string FileName = "Documentation.md";
+
+    public static LoadedDocumentation Load()
+    {
+        foreach (var path in CandidatePaths())
+        {
+            try
+            {
+                if (File.Exists(path))
+                {
+                    return new LoadedDocumentation(File.ReadAllText(path), path);
+                }
+            }
+            catch (IOException)
+            {
+                // try the next candidate
+            }
+        }
+
+        var assembly = typeof(DocumentationLoader).Assembly;
+        using var stream = assembly.GetManifestResourceStream(EmbeddedName);
+        if (stream is null)
+        {
+            return new LoadedDocumentation(
+                "# Documentation\n\nThe user guide file was not found. Add `docs/Documentation.md` to the project.",
+                null);
+        }
+
+        using var reader = new StreamReader(stream);
+        return new LoadedDocumentation(reader.ReadToEnd(), null);
+    }
+
+    public static IEnumerable<string> CandidatePaths()
+    {
+        var baseDir = AppContext.BaseDirectory;
+        yield return Path.Combine(baseDir, FileName);
+        yield return Path.Combine(baseDir, "docs", FileName);
+        var dir = new DirectoryInfo(baseDir);
+        for (var n = 0; n < 8 && dir is not null; n++, dir = dir.Parent)
+        {
+            yield return Path.Combine(dir.FullName, "docs", FileName);
+            yield return Path.Combine(dir.FullName, FileName);
+        }
+    }
+}
+
+public sealed record LoadedDocumentation(string Markdown, string? SourcePath);