Group logging: log on a whole fleet at once, MetaBase style

Apps/MetaWear/MetaWear/App/AppStore.swift

@@ -65,6 +65,19 @@ final class AppStore {
 
     // MARK: - Demo device
 
+    /// Orchestrates group logging (start/stop-and-download across several
+    /// boards). Owned here — never by a view — so an in-flight fleet walk
+    /// survives navigation. Created lazily; solo sessions never pay for it.
+    private var _groupCapture: GroupCaptureCoordinator?
+    var groupCapture: GroupCaptureCoordinator {
+        if let coordinator = _groupCapture { return coordinator }
+        let coordinator = GroupCaptureCoordinator(
+            containers: containers, persistence: persistence, appStore: self
+        )
+        _groupCapture = coordinator
+        return coordinator
+    }
+
     /// The fully simulated MetaWear fleet (see `DemoBLETransport.Identity`).
     /// Created on first access so non-demo sessions never pay for it; each
     /// board is a stable instance reused across connect/disconnect cycles

Apps/MetaWear/MetaWear/App/DemoMode.swift

@@ -31,6 +31,17 @@ enum DemoMode {
         identities.contains { $0.identifier == id }
     }
 
+    /// Display MAC for a demo board (from its transport identity, wire
+    /// order reversed to the usual big-endian colon form); nil otherwise.
+    static func macAddress(for id: UUID) -> String? {
+        guard let identity = identities.first(where: { $0.identifier == id }) else {
+            return nil
+        }
+        return identity.macLSBFirst.reversed()
+            .map { String(format: "%02X", $0) }
+            .joined(separator: ":")
+    }
+
     /// Display name for a demo board ("Simulated MetaWear", "Simulated
     /// MetaWear 2", …); nil for non-demo IDs.
     static func name(for id: UUID) -> String? {

Apps/MetaWear/MetaWear/App/RootView.swift

@@ -1,5 +1,6 @@
 import SwiftUI
 import MetaWear
+import MetaWearPersistence
 
 struct RootView: View {
     @Environment(AppStore.self) private var appStore
@@ -22,6 +23,13 @@ struct RootView: View {
                 .navigationDestination(for: DeviceFeaturePane.self) { pane in
                     pane.destination()
                 }
+                // Declared ONCE at the stack root: SessionHistoryView can
+                // appear more than once per stack (scan-root link + the
+                // group screen's link), and per-instance declarations
+                // triggered SwiftUI's duplicate-destination warning.
+                .navigationDestination(for: MWSessionSnapshot.self) {
+                    SessionDetailView(snapshot: $0)
+                }
             }
         } detail: {
             NavigationStack(path: $path) {
@@ -37,12 +45,21 @@ struct RootView: View {
                         // transition. In regular (iPad) the sidebar is
                         // already showing alongside, so the detail just
                         // sits empty rather than nagging the user.
+                        // Safety net: if this pane ever DOES become the
+                        // visible column in compact (the onChange's flip
+                        // can be swallowed mid-transition), push focus
+                        // back to the sidebar. Harmless in regular width
+                        // — preferredCompactColumn only affects compact.
                         Color.clear
+                            .onAppear { preferredColumn = .sidebar }
                     }
                 }
                 .navigationDestination(for: DeviceFeaturePane.self) { pane in
                     pane.destination()
                 }
+                .navigationDestination(for: MWSessionSnapshot.self) {
+                    SessionDetailView(snapshot: $0)
+                }
             }
         }
         .background {
@@ -62,7 +79,18 @@ struct RootView: View {
             // (e.g. a foreignDownload pushed for the previous board) must
             // not resolve against the next one.
             path = NavigationPath()
-            preferredColumn = newID == nil ? .sidebar : .detail
+            if newID == nil {
+                // Deferred one tick: flipping the compact column in the
+                // SAME transaction as the path reset + the detail content
+                // swapping to the blank pane gets swallowed by
+                // NavigationSplitView — compact users ended up stranded on
+                // an empty detail page with only a Back button (field bug:
+                // tap X to disconnect → blank screen instead of the scan
+                // list).
+                Task { @MainActor in preferredColumn = .sidebar }
+            } else {
+                preferredColumn = .detail
+            }
         }
         .overlay {
             if isConnecting {
@@ -159,6 +187,8 @@ enum DeviceFeaturePane: Hashable {
     case sensorConfig
     case liveStream([SensorSelection])
     case logSession
+    /// MetaBase-style multi-board logging — lives on the sidebar stack.
+    case groupLogging
     case download
     /// The Download screen in foreign-session mode: drains a board whose
     /// logging was started on another device via the anonymous-logger path.
@@ -174,6 +204,7 @@ enum DeviceFeaturePane: Hashable {
         case .sensorConfig:              SensorConfigView()
         case .liveStream(let sels):      LiveStreamView(selections: sels)
         case .logSession:                LogSessionView()
+        case .groupLogging:              GroupLoggingView()
         case .download:                  DownloadView()
         case .foreignDownload(let s):    DownloadView(foreign: s)
         case .sessionHistory:            SessionHistoryView()