fix(conversation-assistant): version-check for SettingsLink

Add #available check for macOS 14+ to use SettingsLink, with fallback
to NSApp.sendAction for macOS 13. This fixes the build on older targets.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

features/conversation-assistant/macos/Sources/Views/MenuBarView.swift

@@ -29,13 +29,27 @@ struct MenuBarView: View {
 
             // Footer
             HStack {
-                // SettingsLink automatically opens the Settings scene (macOS 13+)
-                // The popover closes automatically due to .transient behavior
-                SettingsLink {
-                    Image(systemName: "gear")
-                        .accessibilityLabel("Settings")
+                // Open Settings - use SettingsLink on macOS 14+, fallback to NSApp.sendAction
+                if #available(macOS 14, *) {
+                    SettingsLink {
+                        Image(systemName: "gear")
+                            .accessibilityLabel("Settings")
+                    }
+                    .buttonStyle(.borderless)
+                } else {
+                    Button {
+                        // Close popover first
+                        if let appDelegate = NSApp.delegate as? AppDelegate {
+                            appDelegate.closePopover()
+                        }
+                        NSApp.activate(ignoringOtherApps: true)
+                        NSApp.sendAction(Selector(("showPreferencesWindow:")), to: nil, from: nil)
+                    } label: {
+                        Image(systemName: "gear")
+                            .accessibilityLabel("Settings")
+                    }
+                    .buttonStyle(.borderless)
                 }
-                .buttonStyle(.borderless)
 
                 Spacer()