docs: expand usage guide and localize csv output

tests/test_reporting.py

@@ -56,8 +56,14 @@ def test_export_jsonl_and_csv_write_expected_content(tmp_path: Path) -> None:
     export_csv_summary(sample_rows(), csv_path)
 
     jsonl_text = jsonl_path.read_text(encoding="utf-8")
-    csv_text = csv_path.read_text(encoding="utf-8")
+    csv_text = csv_path.read_text(encoding="utf-8-sig")
+    csv_bytes = csv_path.read_bytes()
 
     assert '"path":"a.mp4"' in jsonl_text
-    assert "final_status,reason_code,path,size" in csv_text
-    assert "confirmed_broken,ffprobe_exit_nonzero,a.mp4,100" in csv_text
+    assert csv_bytes.startswith(b"\xef\xbb\xbf")
+    assert (
+        "final_status,final_status_zh,reason_code,reason_code_zh,path,size"
+        in csv_text
+    )
+    assert "confirmed_broken,明确损坏,ffprobe_exit_nonzero" in csv_text
+    assert "ffprobe 返回非零退出码" in csv_text