ui: the sidebar's tabs become one dock; Measure and Signals by keyboard section; session keeps the dock's state

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

src/layout_store.cpp

@@ -568,8 +568,8 @@ bool load_layout(const std::string& path, LayoutState& out) {
         }
       } else if (key == "measure_stats") {
         st.measure_stats = value == "true";
-      } else if (key == "side_tab") {
-        st.side_tab = strip_quote(value);
+      } else if (key == "dock") {
+        st.dock_shown = value == "true";
       } else if (key.rfind("trigger_", 0) == 0) {
         trigger_key(st.trigger, key.substr(8), strip_quote(value));
       } else if (key == "multicast") {
@@ -740,7 +740,7 @@ bool save_layout(const std::string& path, const LayoutState& state) {
     o << "]\n";
   }
   o << "measure_stats = " << (state.measure_stats ? "true" : "false") << "\n";
-  o << "side_tab = \"" << state.side_tab << "\"\n";
+  o << "dock = " << (state.dock_shown ? "true" : "false") << "\n";
   // The trigger, settings and state both. Written even when it is off: that is the point of it.
   o << "trigger_enabled = " << (state.trigger.enabled ? "true" : "false") << "\n";
   if (!state.trigger.channel.empty()) {