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_light.qss b/ui/style_light.qss
index e0a1987..265894d 100644
--- a/ui/style_light.qss
+++ b/ui/style_light.qss
@@ -6,7 +6,9 @@ QPushButton#runButton { background:#166534; color:#dcfce7; border:1px solid #22c
 QPushButton#runButton:checked { background:#991b1b; border-color:#ef4444; color:#fee2e2; }
 QPushButton#logButton { background:#f1f5f9; color:#64748b; border:1px solid #cbd5e1; border-radius:4px; padding:5px 14px; font-family:"IBM Plex Mono",monospace; min-width:80px; }
 QPushButton#logButton:enabled { color:#1e293b; border-color:#3b82f6; }
+QPushButton#logButton:disabled { background:#f8fafc; color:#94a3b8; border:1px solid #e2e8f0; }
 QPushButton#logButton:checked { background:#fef2f2; border-color:#ef4444; color:#991b1b; }
+QPushButton#logButton[recording="true"] { background:#ef4444; border-color:#fca5a5; color:#ffffff; }
 QPushButton#toolbarSectionBtn { background:#f1f5f9; color:#475569; border:1px solid #cbd5e1; border-radius:4px; padding:5px 14px; font-weight:600; }
 QPushButton#toolbarSectionBtn:hover { background:#e2e8f0; color:#1e293b; }
 QPushButton#toolbarSectionBtn:checked { background:#dbeafe; color:#1d4ed8; border-color:#3b82f6; }