fix: expose per-file cover identities in import scans

backend/tests/test_import_and_model_errors.py

@@ -24,6 +24,8 @@ def test_scan_selected_student_folder_prefills_cover_identity(tmp_path, monkeypa
     assert project["status"] == "needs_confirmation"
     assert len(project["files"]) == 5
     assert project["missing"] == []
+    assert project["folder_identity"] == {"student_no": "", "name": "", "topic": ""}
+    assert all(file["detected_identity"]["student_no"] == "9000000001" for file in project["files"])
     assert scan("test", root=tmp_path)["projects"] == result["projects"]
 
 
@@ -39,6 +41,26 @@ def test_scan_conflicting_covers_need_confirmation(tmp_path, monkeypatch):
     assert project["student_no"] == ""
     assert project["warnings"]
     assert project["status"] == "needs_confirmation"
+    assert "学号" in project["warnings"][0]
+    assert "student_no" not in project["warnings"][0]
+    assert {file["detected_identity"]["student_no"] for file in project["files"]} == {"9000000001", "9000000002"}
+
+
+def test_scan_unreadable_cover_has_no_stale_identity(tmp_path, monkeypatch):
+    from wisegrade import storage
+    folder = tmp_path / "9000000001_学生甲_机器人系统"
+    folder.mkdir()
+    (folder / "阶段报告1.pdf").write_bytes(b"fixture")
+    (folder / "阶段报告2.pdf").write_bytes(b"broken")
+    def read(path):
+        if path.name.endswith("2.pdf"):
+            raise ValueError("损坏PDF")
+        return "学号：9000000001\n姓名：学生甲\n题目：机器人系统"
+    monkeypatch.setattr(storage, "first_text", read)
+    project = scan(".", root=tmp_path)["projects"][0]
+    assert project["folder_identity"]["student_no"] == "9000000001"
+    assert project["files"][0]["detected_identity"]["student_no"] == "9000000001"
+    assert project["files"][1]["detected_identity"] == {}
 
 
 def test_scan_parent_skips_empty_folders(tmp_path, monkeypatch):