docs: the signal badges, the signal pages and the six-badge overflow (step 2 of the redesign)

Also wrap the signals page's hint line, which at 375 px minimum widened the whole slide-over panel to 376.

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

src/ui/signals-panel.ui

@@ -55,6 +55,8 @@
           <object class="GtkLabel" id="signals_hint">
             <property name="label" translatable="yes">click a signal for its page; drag its badge onto a plot</property>
             <property name="halign">start</property>
+            <property name="xalign">0</property>
+            <property name="wrap">1</property>
             <property name="hexpand">1</property>
             <property name="css-classes">dim-label</property>
           </object>

src/ui_tour.cpp

@@ -445,9 +445,10 @@ constexpr TourStep kTourSteps[] = {
      "zooms, a drag pans, and a right-click on a row opens that plot's own menu.",
      &App::area_overlay},
     {"badges", nullptr, "The badges",
-     "Setup is reached by the thing it configures. The Trigger badge opens the trigger form; the "
-     "Source badge opens the source's own controls. Click it again, press Esc or click the plot to "
-     "close the panel.",
+     "Setup is reached by the thing it configures. A badge per signal opens that signal's colour, "
+     "calibration and plot; the + opens the full list; Trigger and Source open their own forms. Drag a "
+     "signal badge onto a plot to draw it there, or onto another badge to reorder. Click again, press "
+     "Esc or click the plot to close the panel.",
      &App::badge_bar},
     {"trigger", "trigger", "The trigger",
      "Describe an event -- a signal, a condition, a level and the window around it -- and arm it: "