ui: the events list is a slide-over page; the left pane, its divider and the header toggle are gone

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/ui_signals.cpp

@@ -656,9 +656,6 @@ GtkWidget* build_signal_panel(App& app) {
   return box;
 }
 
-/// The pane's availability as one reading: the history button on the bar, the pane revealed, and the
-/// switch that decides half of it. Both the button and the pane follow trigger mode *and* recording,
-/// so every step that changes either prints all three.
 /// Whether the signal list's first row still carries its acquire tick. A file view has nothing to
 /// acquire -- the samples are stored -- so the tick goes; in live mode it is the control that decides
 /// what is acquired at all.