Fix FTP regressions and broaden CI coverage

VirtualFS.Tests/Physical/SimpleFtpFileSystemTests.cs

@@ -0,0 +1,23 @@
+using System.IO;
+using VirtualFS.Physical;
+
+namespace VirtualFS.Tests.Physical;
+
+public class SimpleFtpFileSystemTests
+{
+    [Fact]
+    public void DirectoryListingContainsEntryReturnsFalseWhenNameIsMissing()
+    {
+        using var reader = new StringReader("alpha\nbeta\ngamma\n");
+
+        Assert.False(SimpleFtpFileSystem.DirectoryListingContainsEntry(reader, "delta"));
+    }
+
+    [Fact]
+    public void DirectoryListingContainsEntrySkipsDotEntries()
+    {
+        using var reader = new StringReader(".\n..\ntarget\n");
+
+        Assert.True(SimpleFtpFileSystem.DirectoryListingContainsEntry(reader, "target"));
+    }
+}