为二维与三维深度色标增加每帧自适应选项。

默认仍锁定本会话首帧，勾选后两视图按当前帧有效深度共用同一范围。已用深度色标与显示设置测试验证。

shared/src/orisys_app_shared/scene3d/contracts.py

@@ -645,6 +645,11 @@ class DisplaySettings:
     flow_grid_spacing: int = 10
     #: Cap on arrows uploaded per overlay kind.
     max_arrows: int = 400
+    #: Depth colour span for both the 2D canvas and the 3D surface. Off (the default)
+    #: latches the first finite depth of the session so frames stay comparable. On
+    #: refits both views to the current frame's finite minimum and maximum — the
+    #: earlier per-frame colour bar. A fixed colour scale still wins over either.
+    depth_scale_adaptive: bool = False
 
 
 @dataclass(frozen=True)