统一力值阈值处理并保留原始采样

移除自动显示基线，使逐轴阈值统一作用于曲线、读数与记录输出，标定拟合继续使用原始采样。
共享层全量测试和相关 Studio 测试通过。

apps/studio/tests/test_display_prefs.py

@@ -286,28 +286,20 @@ def test_a_partial_plot_settings_mapping_leaves_the_rest_as_stored():
     assert parts["charts"].deadband_floors[-1]["raw"] == 900.0
 
 
-def test_the_display_baseline_is_not_a_finger_only_setting():
-    """Every sensor type and both units: an idle newton offset is the same problem."""
+def test_force_threshold_policy_is_available_for_each_sensor_and_unit():
     for sensor, units in (("box", "newton"), ("box", "raw"),
                           ("finger", "newton"), ("finger", "raw")):
-        controller, parts = _controller(prefs={"raw_auto_zero": True},
-                                        sensor_type=sensor, units=units)
+        controller, parts = _controller(sensor_type=sensor, units=units)
         assert parts["charts"].presentation_enabled[-1] is True, (sensor, units)
         assert parts["charts"].presentation[-1]["unit"] == (
             "N" if units == "newton" else "raw"
         )
 
-    controller, parts = _controller(prefs={"raw_auto_zero": False}, sensor_type="box",
-                                    units="newton")
-    assert parts["charts"].presentation_enabled[-1] is False
-
-
 def test_the_deadband_floors_reach_the_charts_from_the_preferences():
     controller, parts = _controller(prefs={"plot_deadband_n": 0.5, "plot_deadband_raw": 2000.0})
     assert parts["charts"].deadband_floors[-1] == {"newton": 0.5, "raw": 2000.0}
 
-    controller.set_raw_auto_zero(True)  # re-applies the whole policy
-    assert parts["charts"].deadband_floors[-1] == {"newton": 0.5, "raw": 2000.0}
+    assert parts["charts"].presentation_enabled[-1] is True
 
 
 def test_the_sample_rate_prefers_the_measured_rate_over_the_stored_one():