Fix voice note fragment handling and narrow macOS sidebar

- Fix fragment processing bug where fragments were logged but not handled
- Remove redundant 'Processing fragment directly' check that prevented handling
- Make macOS sidebar narrower (300px max or 40% of width, whichever is smaller)
- iOS sidebar remains at 70% width for better touch interaction

bitchat/Views/ContentView.swift

@@ -85,7 +85,11 @@ struct ContentView: View {
                             }
                         
                         sidebarView
+                            #if os(macOS)
+                            .frame(width: min(300, geometry.size.width * 0.4))
+                            #else
                             .frame(width: geometry.size.width * 0.7)
+                            #endif
                             .transition(.move(edge: .trailing))
                     }
                     .offset(x: showSidebar ? -sidebarDragOffset : geometry.size.width - sidebarDragOffset)