三维显示与二维共用深度色标，配置名改为 Finger

箭头阈值写入设置；去掉网格告警。三维色标改为立刻采用二维量程（不再 P5/P95 缓变）。选择器显示 Finger。已用 pane UI、shared-scale 与 catalog 单测验证。

apps/studio/tests/test_shared_depth_scale.py

@@ -43,12 +43,10 @@ def test_depth_without_a_shared_span_still_measures_the_field() -> None:
     field = _field("depth_response", np.linspace(0.0, 9.0, 16).reshape(4, 4))
     span = _field_scalar_range(
         field,
-        previous=None,
+        previous=(0.0, 2.0),
         shared_depth_scale=None,
     )
-    assert span is not None
-    assert span[0] == 0.0
-    assert span[1] > 1.0
+    assert span == (0.0, 9.0)
 
 
 def test_a_degenerate_shared_span_falls_back_to_the_measurement() -> None: