fix the finger 2D canvas orientation and the 3D arrow size

The unrolled canvas put the finger's +x where the 3D default view puts screen-left,
and the 3D flow arrows rasterised as 0.23 px hairlines because their stroke was 2 %
of their own sub-millimetre length. The 2D presentation is now the derived half turn
(persisted, set from the plot-settings dialog) and the 3D stroke is one canvas pixel
— the width the 2D canvas draws — verified numerically and with real-GL snapshots.

apps/studio/config/locales/zh_CN.json

@@ -73,6 +73,14 @@
     "plot_deadband_raw": "归零阈值（原始）",
     "plot_deadband_raw_tip": "原始模式下的显示死区下限（原始计数）。0 = 自动（默认下限 50 计数）。标定数据可疑时可手动放大，只影响显示",
     "reset_defaults": "恢复默认",
+    "plot_orientation_group": "手指 2D 显示方向（只影响 2D 画面；3D 视图仍用设计坐标系）",
+    "plot_orientation": "方向",
+    "plot_orientation_tip": "手指 2D 画布（展开域）的显示方向。默认 180° 是按展开图与设计坐标系推导出来的：画布的 +x 是设计系的 +X、屏幕向上是 −Z，与 3D 默认视图的 −X / +Z 正好都相反，所以要把画面转半圈，箭头左右才与 3D 一致。只影响显示，不改变记录与存储的数组",
+    "plot_orientation_note": "只影响 2D 手指画布的显示：存储的光流、有效掩膜与录制数据始终保持域本身的朝向。3D 视图不受影响（它的坐标系是设计导出坐标系）",
+    "orientation_identity": "原始（不旋转）",
+    "orientation_rotate180": "旋转 180°（默认）",
+    "orientation_mirror_h": "水平镜像",
+    "orientation_mirror_v": "垂直镜像",
     "plot_filters": "滤波（作用于采集，界面与记录同步）",
     "filter_preset": "预设",
     "filter_preset_tip": "选择一档现成的滤波组合；改下面任一数值会变成“自定义”",