Fix test that leaks a chdir'd cwd across the test run (#17)

test_relative_symlink_to_common_file changed the process working
directory via os.chdir() but never restored it, leaving subsequent
tests running from a tmp_path fixture directory that gets deleted
after the test. Restore cwd in a finally block, matching the pattern
already used in test_pseudo_direntry.py.

Also checks off the now-satisfied xfail-marker item: no xfail markers
remain in the repo.

Co-authored-by: Maxim Shulga <maxim.shulga@alludo.com>
Co-authored-by: Claude Sonnet 5 <noreply@anthropic.com>

tests/test_fs.py

@@ -48,8 +48,12 @@ class TestHardlinkDir:
         src_dir, dst_dir = hardlink_dirs
         cf_relpath = relpath(create_file(src_dir), src_dir, dst_dir)
         sl2cf_relpath = "symlink_to_common_file"
-        os.chdir(src_dir)
-        os.symlink(cf_relpath, sl2cf_relpath)
+        original_cwd = os.getcwd()
+        try:
+            os.chdir(src_dir)
+            os.symlink(cf_relpath, sl2cf_relpath)
+        finally:
+            os.chdir(original_cwd)
 
         fs.hardlink_dir(src_dir, dst_dir)