调整 Autocal 标定记录格式与目录命名

将人工参考载荷按档位区间保存，重排帧字段并明确界面操作。已通过相关测试、代码和文档检查。

apps/autocal/config/locales/en_US.json

@@ -263,6 +263,7 @@
     "frame": "Frame {frame} · source {source_frame} · {basis} {time} · dropped {dropped}"
   },
   "calibration": {
+    "sensor_model": "Product model",
     "sensor_sn": "Sensor SN",
     "output": "Output directory",
     "site_view": "Select site",
@@ -272,13 +273,15 @@
     "levels": "Load levels (N)",
     "hold": "Suggested hold",
     "reference": "Actual reference (N)",
-    "start": "Start recording",
-    "confirm": "Confirm level",
-    "finish": "Finish trial",
+    "start": "Start trial recording",
+    "confirm": "Confirm current level",
+    "finish": "Finish and save",
     "abort": "Abort and keep data",
     "load": "Load",
     "unload": "Unload",
     "next_step": "Next: {branch} to {load:g} N",
+    "before_start": "Start trial recording first",
+    "ready_to_finish": "All levels confirmed; finish and save",
     "no_step": "No step pending",
     "progress": "Progress {done}/{total} · {status}",
     "held": " · Current level held {seconds:.1f} s",