feat: 进度改为目录轮询驱动, 每秒刷新 (绕过后端输出缓冲, stdbuf在Android无效)

tests/test_transfer.py

@@ -270,3 +270,15 @@ def test_speed_stats_empty():
 def test_speed_stats_single():
     cur, peak, avg = transfer.speed_stats([8 * 1024 * 1024])
     assert (cur, peak, avg) == (8 * 1024 * 1024, 8 * 1024 * 1024, 8 * 1024 * 1024)
+
+# ---------- 目录大小轮询 (rsync 输出缓冲替代方案) ----------
+
+def test_dir_size_returns_bytes(tmp_path):
+    """du 目录返回字节数"""
+    (tmp_path / "a.bin").write_bytes(b"x" * 1000)
+    (tmp_path / "sub").mkdir()
+    (tmp_path / "sub" / "b.bin").write_bytes(b"y" * 500)
+    assert transfer.dir_size(str(tmp_path)) == 1500
+
+def test_dir_size_missing_returns_zero():
+    assert transfer.dir_size("/nonexistent/path/xyz") == 0