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/en_US.json

@@ -73,6 +73,14 @@
     "plot_deadband_raw": "Zero threshold (raw)",
     "plot_deadband_raw_tip": "Display deadband floor in raw mode (raw counts). 0 = auto (the built-in 50-count floor). Raise it by hand when the calibration data is suspect; display only",
     "reset_defaults": "Reset to defaults",
+    "plot_orientation_group": "Finger 2D presentation (2D only; the 3D view keeps the design frame)",
+    "plot_orientation": "Orientation",
+    "plot_orientation_tip": "How the finger's 2D canvas (the unrolled domain) is presented. The 180° default is derived from the unroll map and the design frame: the canvas's +x is the frame's +X and its screen up is −Z, while the 3D default view puts −X right and +Z up, so both axes are reversed and a half turn is what makes the arrows agree left-to-right. Display only — the record and the stored arrays are untouched",
+    "plot_orientation_note": "Affects the 2D finger canvas only: the stored flow, valid mask and recorded data keep the domain's own orientation. The 3D view is not affected (its frame is the design export's)",
+    "orientation_identity": "As drawn (no rotation)",
+    "orientation_rotate180": "Rotate 180° (default)",
+    "orientation_mirror_h": "Mirror horizontally",
+    "orientation_mirror_v": "Mirror vertically",
     "plot_filters": "Filters (applied while acquiring; screen and record agree)",
     "filter_preset": "Preset",
     "filter_preset_tip": "A ready-made combination; editing any value below switches to Custom",