Sync Mark-10 gauge's live unit into ChannelConfig instead of a fixed default

Mark10Layer._parse() already tracked whichever unit suffix the gauge
last reported (lb/kgF/N/ozF — the gauge's physical unit button cycles
these independently of this app). serial_device.py hardcoded the
"force" channel's unit to "N" and never updated it, so switching units
on the gauge itself was invisible here.

Adds Mark10Layer.current_unit and has SerialDevice.read_channels()
keep the "force" ChannelConfig's unit in sync with it on every poll.
This fixes the unit shown in anything that reads ChannelConfig.unit
live — new plots, channel pickers, CSV log headers — but does not
relabel the Y-axis of an already-open plot pane, since plot axis
labels are baked into PlotConfig.y_label once at plot-build time, not
re-read from the channel live. Making an open pane's axis relabel
itself would need new signal plumbing from the device through
AcquisitionEngine to the strip chart — a bigger, separate change.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

1 files changed, 8 insertions, 0 deletions

diff --git a/devices/serial_device.py b/devices/serial_device.py
index 067656a..eadaa42 100644
--- a/devices/serial_device.py
+++ b/devices/serial_device.py
@@ -142,6 +142,14 @@ class SerialDevice(BaseDevice):
         raw = self._layer.read()
         if not raw:
             return {}
+        if self._fmt == "mark10" and hasattr(self._layer, "current_unit"):
+            # Gauge can be switched between lb/kgF/N/ozF on the device itself —
+            # keep the channel's unit in sync so new plots/pickers/CSV log
+            # headers pick up the currently-selected unit instead of a fixed
+            # default. Does not relabel the axis of an already-open plot pane.
+            force_ch = self.get_channel("force")
+            if force_ch is not None:
+                force_ch.unit = self._layer.current_unit
         if self._fmt not in _GENERIC_FORMATS:
             # Protocol layers already key by channel_id — pass through untouched.
             # (Write-only channels, e.g. CML "M1_VS", never appear in raw — correctly dropped.)