统一实时标定身份解析并规范行尾

控制器与两个对话框共用 CalibrationService.read_identity，解析失败与缺 SN 分开上报；
本轮改动文件统一 LF，SN 必填回归已锁定。
定向 73 项、校准 UI 8 项与 lint 通过；未跑全量门禁。

apps/studio/tests/test_calibration_service.py

@@ -79,3 +79,52 @@ def test_the_same_configuration_named_differently_is_not_a_mismatch(tmp_path):
 
     # ...but it does have to be a path: a non-path value simply differs.
     assert CalibrationService.same_path("D:/lab/a/sensor.json", "not a path\x00") is False
+
+
+# --------------------------------------------------- one parse, both answers
+
+
+def test_read_identity_returns_the_identity_and_no_error(tmp_path):
+    """The strict parse answers with the identity *and* says it succeeded."""
+    path = _calibration_file(tmp_path, sensor_type="box", config_ref="D:/lab/a/sensor.json")
+
+    identity, error = CalibrationService.read_identity(path)
+
+    assert error == ""
+    assert identity == {
+        "sensor_type": "box",
+        "sn": "SN-A",
+        "config_ref": "D:/lab/a/sensor.json",
+    }
+    # The old name keeps its behaviour and is a thin wrapper over the one parse.
+    assert CalibrationService.identity_of(path) == identity
+
+
+def test_read_identity_keeps_the_parsers_reason_when_the_file_cannot_be_read(tmp_path):
+    broken = tmp_path / "broken.json"
+    broken.write_text(
+        json.dumps({"schema_version": 2, "unit": "N", "channels": {"fn": "bogus"}}),
+        encoding="utf-8",
+    )
+
+    identity, error = CalibrationService.read_identity(broken)
+
+    assert identity == {}
+    assert error
+    assert "\n" not in error, "the reason must stay one line for the status bar"
+    assert CalibrationService.identity_of(broken) == {}
+
+
+def test_read_identity_distinguishes_a_parsed_document_without_an_sn(tmp_path):
+    """A readable document that simply names no device is not a parse failure."""
+    path = _calibration_file(tmp_path, sensor_type="box", config_ref="D:/lab/a/sensor.json")
+    document = json.loads(path.read_text(encoding="utf-8"))
+    document.pop("identity")
+    document.pop("pipeline")
+    path.write_text(json.dumps(document), encoding="utf-8")
+
+    identity, error = CalibrationService.read_identity(path)
+
+    assert error == ""
+    assert identity["sn"] == ""
+    assert identity["sensor_type"] == ""