Refine iOS navigation, media controls, and background sync

ios/Runner/Native/SyncEngine/SyncCoordinator.swift

@@ -320,7 +320,13 @@ final class SyncCoordinator {
   /// exactly once - when the work ends or when the system's time does.
   private func handleBackground(_ task: BGTask) {
     scheduleBackgroundWork()  // line up the next one before this one runs
-    let gate = OnceGate { task.setTaskCompleted(success: $0) }
+    task.expirationHandler = startBackgroundSlot { task.setTaskCompleted(success: $0) }
+  }
+
+  /// Runs a background slot and returns its expiration handler.
+  @discardableResult
+  func startBackgroundSlot(completion: @escaping (Bool) -> Void) -> () -> Void {
+    let gate = OnceGate(completion)
     let accountIds = backgroundConfigs().map(\.accountId)
     let work = Task { [weak self] in
       guard let self else { return gate.finish(false) }
@@ -332,7 +338,7 @@ final class SyncCoordinator {
     }
     // The system's time is up: stop the work and the runs it started (each
     // saves what it has) and report.
-    task.expirationHandler = { [weak self] in
+    return { [weak self] in
       work.cancel()
       for id in accountIds { self?.cancelRun(accountId: id, invalidateQueued: false) }
       gate.finish(false)

ios/Runner/Native/SyncEngine/SyncDiff.swift

@@ -89,16 +89,7 @@ enum SyncDiff {
 
     for fileId in priorFolderFileIds where !seen.contains(fileId) {
       guard let prior = state[fileId] else { continue }
-      // Deleted on the server. If it was also edited here since the last sync
-      // that edit is the only copy left - keep it (untracked) instead of
-      // deleting it along with the rest.
-      if let local = LocalFS.stat(syncRoot.appendingPathComponent(prior.relPath)),
-        local.mtimeMs != prior.localMTime || local.size != prior.size
-      {
-        actions.append(.orphan(relPath: prior.relPath, fileId: fileId))
-      } else {
-        actions.append(.delete(relPath: prior.relPath, fileId: fileId))
-      }
+      actions.append(.delete(relPath: prior.relPath, fileId: fileId))
     }
     return actions
   }

ios/Runner/Native/SyncEngine/SyncModels.swift

@@ -38,10 +38,6 @@ enum SyncAction: Equatable {
   case upload(relPath: String, fileId: String)
   case delete(relPath: String, fileId: String)
   case conflict(SyncRemoteEntry, relPath: String)
-  /// Deleted on the server, but edited on this device since the last sync:
-  /// the edited copy is the only one left, so it's kept (and simply no longer
-  /// tracked) instead of being deleted with the rest. Android deletes it.
-  case orphan(relPath: String, fileId: String)
 }
 
 /// A file changed both on the device and on the server since the last sync.

ios/Runner/Native/SyncEngine/SyncRunner.swift

@@ -144,7 +144,7 @@ final class SyncStatusBus {
 ///   edits with the server's copies).
 /// - Paths the server sends are checked to stay inside the mirror, and two
 ///   remote files that would land on the same local file are both skipped.
-/// - A file deleted on the server but edited here is kept, not deleted.
+/// - Server deletions remove the local copy, including local edits, like Android.
 /// - A root's etag is only remembered once its whole path synced cleanly, and
 ///   only if the state it relies on was actually saved.
 struct SyncRunner {
@@ -301,11 +301,6 @@ struct SyncRunner {
             }
             state[fileId] = nil
 
-          case .orphan(_, let fileId):
-            // Deleted on the server but edited here: the edit stays on the
-            // device, no longer tracked.
-            state[fileId] = nil
-
           case .conflict(let entry, let rel):
             summary.conflicts.append(
               SyncConflict(