Make the rail reset zero the sensor in live and the display in replay

The replay view disabled a control whose display reset is exactly what an
operator wants there, and the bare "Reset" hid that the live one zeroes the
sensor tracker; the label, tooltip and status line now name the target, and
Ctrl+R follows the view. Verified with the studio suite, ui_check (628
checks) and real-GL rail snapshots of both views.

apps/studio/config/locales/en_US.json

@@ -45,7 +45,8 @@
     "run": "Run / Stop",
     "stop": "Cancel acquisition",
     "preview": "Preview / Stop preview",
-    "reset": "Reset tracker",
+    "reset": "Reset sensor tracker",
+    "reset_display": "Reset display",
     "reset_view": "Reset views",
     "reset_view_tip": "Put the chart window, cursor and 3D camera back to their defaults (F8). Touches neither the device nor the zero estimate.",
     "pause": "Pause / resume (F7)",
@@ -133,8 +134,11 @@
     "playback_disabled": "Open a recorded video first (“Choose a recorded video…” at the top left)",
     "playback_needs_recording": "This video has no recording beside it (no forces.csv): replay needs a recording; to just watch the video use View ▸ Recompute forces from the video",
     "playback_video_only": "Play this video (no recording beside it: the picture plays, the force charts are empty)",
-    "reset": "Reset",
-    "reset_tip": "Zero the device tracker. This affects the zero point only, never the view — to put the views back use View → Reset views.",
+    "reset_sensor": "Reset sensor",
+    "reset_sensor_tip": "Zero the sensor tracker (the device's own zero). Zeroing it also restarts the display baseline, so the curves and the value cards re-learn their zero from the next quiet samples; the curve history is kept — View ▸ Reset views (F8) clears the views.",
+    "reset_sensor_unavailable": "Zero the sensor tracker — available while a session is running (start a run first).",
+    "reset_display": "Reset display",
+    "reset_display_tip": "Clear the accumulated display: the curves, cursor and value cards go back to their defaults and the replay returns to the start of the recording. There is no device session in this view, so nothing of the device is touched; the 3D camera is View ▸ Reset views (F8).",
     "pause": "⏸  Pause",
     "pause_resume": "▶",
     "pause_tip": "Pause the computation and the display (F7): no flow, depth or contact is computed, the picture holds its last frame, and the device stays connected for an immediate resume. A recording that spans a pause has a gap.",
@@ -424,8 +428,9 @@
     "capture_slow": "The camera delivers less than the configured frame rate: {detail}. The recording keeps the real rate. This is a capture-side (camera/driver) matter that software cannot change: use a camera that really does deliver 30 fps — after checking that the cable or port is not slowing this one down — and measure again.",
     "video_ended": "Video ended",
     "camera_disconnected": "Camera disconnected",
-    "reset_ok": "Tracker reset",
-    "reset_pending": "Zeroing requested; waiting for the acquisition thread to confirm…",
+    "reset_ok": "Sensor tracker reset (the display baseline restarts)",
+    "reset_pending": "Sensor zero requested; the display baseline restarts once the acquisition thread confirms…",
+    "reset_display": "Display reset: curves back to their defaults, replay at the start",
     "view_reset": "Views reset",
     "paused": "Paused: nothing is computed, the device stays connected",
     "resumed": "Resumed",