fix(ios): reconnect to Mac when returning to the foreground

Reported as "Code Island Buddy keeps disconnecting when app minimized or
iPhone closed" (#261). Root cause: the MultipeerConnectivity session that
carries the rich, foreground status (the "Mac connected" state ContentView
shows) is torn down by iOS whenever the app is backgrounded or the phone
is locked — that part is expected, standard platform behavior for
Wi-Fi/Bonjour-based connectivity, not a bug, and it's exactly why a
separate Bluetooth channel already exists for background Live
Activity/Watch summaries (bluetooth-central is already declared in
Info.plist and works as designed).

The actual bug: nothing ever told the browser to restart afterwards.
`ContentView`'s `.onAppear { connection.start() }` runs once, when the
view first appears, not on every return to the foreground, and `start()`
itself no-ops once `browsing` is already (stale-)true. So after any
background/foreground cycle the app was stuck showing "disconnected"
until the user manually tapped the search toggle — indistinguishable from
"keeps disconnecting" to a user who never touches that button.

Fix: observe `scenePhase` at the App level and, only on a real
background -> active transition (not initial launch) with no connected
peer, force a clean stop()+start() of discovery. No-ops whenever the
connection is already healthy.

Verified via full `xcodebuild` (all targets, complete embedded app).

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

Author: wxtsky

ios/CodeIslandCompanion/CodeIslandCompanion/CodeIslandCompanionApp.swift

@@ -4,6 +4,7 @@ import SwiftUI
 struct CodeIslandCompanionApp: App {
     @StateObject private var connection: CompanionConnection
     @StateObject private var liveActivity: LiveActivityController
+    @Environment(\.scenePhase) private var scenePhase
 
     init() {
         let connection = CompanionConnection()
@@ -26,6 +27,13 @@ struct CodeIslandCompanionApp: App {
                 .environmentObject(connection)
                 .environmentObject(liveActivity)
         }
+        // MultipeerConnectivity sessions don't survive backgrounding; without
+        // this, returning to the foreground after minimizing the app or
+        // locking the phone left it stuck showing "disconnected" (#261).
+        .onChange(of: scenePhase) { oldPhase, newPhase in
+            guard oldPhase == .background, newPhase == .active else { return }
+            connection.reconnectIfNeeded()
+        }
     }
 
 #if DEBUG

ios/CodeIslandCompanion/CodeIslandCompanion/CompanionConnection.swift

@@ -100,6 +100,26 @@ final class CompanionConnection: NSObject, ObservableObject {
         pendingReconnectPeer = nil
     }
 
+    /// MultipeerConnectivity sessions are torn down by iOS while the app is
+    /// backgrounded — unlike Bluetooth, Wi-Fi/Bonjour connectivity has no
+    /// platform-level background continuation, so this is expected, not a bug
+    /// (#261). The problem is that nothing ever told the browser to restart:
+    /// `ContentView`'s `.onAppear { connection.start() }` only fires once, when
+    /// the view first appears, not on every return to the foreground, and
+    /// `start()` no-ops while `browsing` is already (stale-)true. So once the
+    /// session drops in the background, the app was stuck showing
+    /// "disconnected" until the user manually tapped the search toggle.
+    ///
+    /// Call this from a scene-phase observer whenever the app becomes active
+    /// again; it forces a clean restart of discovery only when we're not
+    /// already connected, so it's a no-op for an already-healthy connection.
+    func reconnectIfNeeded() {
+        guard !isDemoMode, mockStatePayload == nil else { return }
+        guard connectedPeer == nil else { return }
+        stop()
+        start()
+    }
+
     func connect(to peer: MCPeerID) {
         exitDemoMode()
         browser.invitePeer(peer, to: session, withContext: nil, timeout: 12)