ios: derive the switch outcome from the active user instead of a flag

The one-time link picker's old-core fallback set selectedProfile to the new user
unconditionally, but the resync it does first is wrapped in a catch - so when the switch
threw, the picker put its checkmark on a profile that is not active and cannot be
selected, because the view then thinks it is already selected. Reading
chatModel.currentUser instead is right in both cases and is a line shorter.

The compose picker had the same question answered with a local switched flag. The active
user answers it there too, which removes the flag, the two assignments that set it, and
with them the mutable-local-in-a-@Sendable-closure problem that flag caused when it was
first introduced.

apps/ios/Shared/Views/Chat/ComposeMessage/ContextProfilePickerView.swift

@@ -269,19 +269,19 @@ struct ContextProfilePickerView: View {
         if newUser.activeUser {
             // An older remote host ignored keepActiveUser, so the reassignment would
             // fail. Resync and report - not rethrown, or the form blames the creation.
-            let switched: Bool
             do {
                 try await changeActiveUserAsync_(newUser.userId, viewPwd: nil)
-                switched = true
             } catch {
                 logger.error("changeActiveUserAsync_ error: \(responseError(error))")
-                switched = false
             }
             await MainActor.run {
                 // Unconditional: the switch only removes this view when it succeeded
                 showAddProfile = false
-                // Only if it switched: the chat is then gone from the list and renders blank
-                if switched && chatModel.chatId == chat.id { chatModel.chatId = nil }
+                // Only if it switched, which the active user tells us: the prepared chat
+                // is then gone from the reloaded list and would render blank.
+                if chatModel.currentUser?.userId == newUser.userId && chatModel.chatId == chat.id {
+                    chatModel.chatId = nil
+                }
             }
             alertAfterDismissal(NSLocalizedString("Error changing chat profile", comment: "alert title"))
             return

apps/ios/Shared/Views/NewChat/NewChatView.swift

@@ -610,9 +610,11 @@ private struct ActiveProfilePicker: View {
             // with the previous one, so a second attempt would fail the same way.
             await MainActor.run {
                 showAddProfile = false
-                // Make the picker agree with the profile that is now active
                 profileSwitchStatus = .idle
-                selectedProfile = newUser
+                // Whatever the resync above ended up with - newUser if it switched, the
+                // previous profile if it threw. Not newUser unconditionally, or a failed
+                // switch leaves the checkmark on a profile that is not active.
+                selectedProfile = chatModel.currentUser ?? selectedProfile
             }
             alertAfterDismissal(NSLocalizedString("Error changing chat profile", comment: "alert title"))
             return