feat(ui): repo scan discovers nested repos in subfolders

RepoScanner.Scan now recurses into subdirectories (max depth 5) instead
of only checking the immediate children of the chosen folder. A found
repo (.git as dir or file) is added without descending further; the
selected folder itself is checked too. Skips node_modules/bin/obj/.git/
.vs/packages and reparse points (junctions/symlinks). Per-directory
IOException/UnauthorizedAccessException no longer aborts the whole scan.

tests/ClaudeDo.Ui.Tests/RepoScannerTests.cs

@@ -57,7 +57,7 @@ public sealed class RepoScannerTests : IDisposable
     }
 
     [Fact]
-    public void Scan_IsNotRecursive()
+    public void Scan_FindsRepoAtDepthTwo()
     {
         var nested = MakeDir(Path.Combine("outer", "inner"));
         Directory.CreateDirectory(Path.Combine(nested, ".git"));
@@ -65,6 +65,47 @@ public sealed class RepoScannerTests : IDisposable
 
         var result = RepoScanner.Scan(_root);
 
+        Assert.Single(result);
+        Assert.Equal("inner", result[0].Name);
+        Assert.Equal(nested, result[0].FullPath);
+    }
+
+    [Fact]
+    public void Scan_FindsRepoAtDepthThree()
+    {
+        var nested = MakeDir(Path.Combine("customers", "projX", "repo"));
+        Directory.CreateDirectory(Path.Combine(nested, ".git"));
+
+        var result = RepoScanner.Scan(_root);
+
+        Assert.Single(result);
+        Assert.Equal("repo", result[0].Name);
+        Assert.Equal(nested, result[0].FullPath);
+    }
+
+    [Fact]
+    public void Scan_DoesNotDescendBelowAFoundRepo()
+    {
+        var repo = MakeDir("repo-a");
+        Directory.CreateDirectory(Path.Combine(repo, ".git"));
+        var submodule = Path.Combine(repo, "vendor", "nested-repo");
+        Directory.CreateDirectory(submodule);
+        Directory.CreateDirectory(Path.Combine(submodule, ".git"));
+
+        var result = RepoScanner.Scan(_root);
+
+        Assert.Single(result);
+        Assert.Equal("repo-a", result[0].Name);
+    }
+
+    [Fact]
+    public void Scan_SkipsNodeModules()
+    {
+        var nodeModules = MakeDir(Path.Combine("node_modules", "some-package"));
+        Directory.CreateDirectory(Path.Combine(nodeModules, ".git"));
+
+        var result = RepoScanner.Scan(_root);
+
         Assert.Empty(result);
     }
 
@@ -75,4 +116,34 @@ public sealed class RepoScannerTests : IDisposable
 
         Assert.Empty(result);
     }
+
+    [Fact]
+#pragma warning disable CA1416 // ACL manipulation is Windows-only; this test targets the Windows dev/CI environment
+    public void Scan_ContinuesAfterUnreadableSubdirectory()
+    {
+        var repo = MakeDir("repo-a");
+        Directory.CreateDirectory(Path.Combine(repo, ".git"));
+        var locked = new DirectoryInfo(MakeDir("locked"));
+        var denyRule = new System.Security.AccessControl.FileSystemAccessRule(
+            Environment.UserName,
+            System.Security.AccessControl.FileSystemRights.ListDirectory,
+            System.Security.AccessControl.AccessControlType.Deny);
+        var acl = locked.GetAccessControl();
+        acl.AddAccessRule(denyRule);
+        try
+        {
+            locked.SetAccessControl(acl);
+
+            var result = RepoScanner.Scan(_root);
+
+            Assert.Single(result);
+            Assert.Equal("repo-a", result[0].Name);
+        }
+        finally
+        {
+            acl.RemoveAccessRule(denyRule);
+            locked.SetAccessControl(acl);
+        }
+    }
+#pragma warning restore CA1416
 }