Make Run the master stop switch; add Log button disabled/recording styling

Run/Stop previously only paused acquisition — control outputs (motor
speed, switches, PWM duty) kept whatever value was last written, so
stopping the run loop didn't stop a running motor. Adds
ControlWidget.safe_stop() (per-widget override, default zeros the
output) and ControlPanel.safe_stop_all(), called from _toggle_run's
Stop branch before engine.stop().

Per-widget behavior is deliberately not uniform:
- OnOffSwitch/MotorControl/PwmControl have a latched running/enabled
  state, so safe_stop() drives their own toggle handler (consistent UI
  + write in one path) and, for Motor/PWM, zeroes the slider too.
- SetpointControl/AnalogOutputControl only write on an explicit user
  action and have no universally safe forced value (e.g. 0 isn't
  necessarily "off" for an arbitrary process setpoint or analog
  output) — Stop leaves them untouched rather than guessing.

Log button: added a :disabled QSS rule so "can't log yet" reads as
clearly inert rather than a duller version of the enabled look, and a
600ms blink (toggling a "recording" dynamic property the QSS keys off)
while a recording is active, so it reads as live/recording rather than
a static pressed button. Master Stop now calls _toggle_log(False)
explicitly when forcing the button off, since QPushButton.setChecked()
doesn't emit clicked — without this the blink would keep running after
a master Stop even though logging itself already halted via
engine.stop()'s internal stop_logging() call.

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

1 files changed, 2 insertions, 0 deletions

diff --git a/ui/style_dark.qss b/ui/style_dark.qss
index e562365..9fd7198 100644
--- a/ui/style_dark.qss
+++ b/ui/style_dark.qss
@@ -63,7 +63,9 @@ QPushButton#logButton {
     min-width: 80px;
 }
 QPushButton#logButton:enabled { color: #e2e8f0; border-color: #3b82f6; }
+QPushButton#logButton:disabled { background-color: #12172a; color: #3d4a6b; border: 1px solid #1e2740; }
 QPushButton#logButton:checked { background-color: #7c2d12; border-color: #ef4444; color: #fee2e2; }
+QPushButton#logButton[recording="true"] { background-color: #ef4444; border-color: #fca5a5; color: #ffffff; }
 
 QPushButton#addDeviceButton {
     background-color: #1e3a5f;