fix: stop the device picker hanging on an offer

Two causes. The connect step had no timeout, so an unreachable device was
retried indefinitely instead of falling through to hold-for-later; it now
gives up after 15s and holds the offer as designed.

The picker also waited on the whole exchange, which includes a person on the
other device deciding — up to two minutes. It now closes on tap and reports
the outcome as a message, and a decline or an unanswered offer is shown as
information rather than an error, since the offer did arrive.

apple/VniDrop/Features/Contacts/ContactsModel.swift

@@ -345,6 +345,14 @@ final class ContactsModel: ObservableObject {
 		}
 	}
 
+	/// Fire-and-report variant of ``offerTransfer(transferId:to:)``.
+	///
+	/// Owned by the model rather than a view so the request survives the picker
+	/// being dismissed: the answer depends on a person at the other device.
+	func offerTransferInBackground(transferId: UInt64, to contact: DeviceContact) {
+		Task { await offerTransfer(transferId: transferId, to: contact) }
+	}
+
 	/// Push an existing transfer to a remembered device.
 	///
 	/// Returns whether it landed, so the caller can distinguish "accepted" from
@@ -365,6 +373,15 @@ final class ContactsModel: ObservableObject {
 			messages.tryShow(UiMessage(text: text, tone: outcome.delivered ? .success : .info))
 			await refresh()
 			return outcome.delivered
+		case .failure(let error) where error.offerRefusal != nil:
+			// The offer was delivered and a person said no, or nobody answered.
+			// Neither is a failure of this device, so neither is shown as one.
+			let text = error.offerRefusal == .declined
+				? L10n.Contacts.declinedByDevice(device: contact.displayName)
+				: L10n.Contacts.noAnswer(device: contact.displayName)
+			messages.tryShow(UiMessage(text: .dynamic(text), tone: .info))
+			await refresh()
+			return false
 		case .failure(let error):
 			messages.error(error)
 			return false

apple/VniDrop/Features/Contacts/DevicePickerSheet.swift

@@ -31,10 +31,12 @@ struct DevicePickerSheet: View {
 				} else {
 					List(reachable) { contact in
 						Button {
-							Task {
-								await model.offerTransfer(transferId: transferId, to: contact)
-								dismiss()
-							}
+							// Close first. The other device's user has to accept,
+							// which can take as long as they take, and holding a
+							// modal open on someone else's decision reads as a
+							// hang. The outcome arrives as a message instead.
+							dismiss()
+							model.offerTransferInBackground(transferId: transferId, to: contact)
 						} label: {
 							HStack {
 								VStack(alignment: .leading, spacing: 2) {
@@ -49,7 +51,7 @@ struct DevicePickerSheet: View {
 								}
 							}
 						}
-						.disabled(!model.state.busyEndpoints.isEmpty)
+						.disabled(model.state.busyEndpoints.contains(contact.endpointId))
 					}
 				}
 			}

apple/VniDrop/UI/Feedback/UserFacingError.swift

@@ -3,6 +3,12 @@ import VnidropCore
 
 /// Maps technical failures to stable, user-facing catalog keys. Ported from
 /// `ui/feedback/UserFacingError.kt`. Never exposes raw `reason=` blobs.
+/// How an offered transfer ended without being accepted.
+enum OfferRefusal {
+	case declined
+	case noAnswer
+}
+
 extension Error {
 	func toUiText() -> UiText {
 		if let invitation = self as? InvitationError {
@@ -57,6 +63,19 @@ extension Error {
 			|| haystack.contains("user canceled")
 	}
 
+	/// The other device answered, and the answer was no.
+	///
+	/// Not a failure of this device: the offer was delivered and a person
+	/// declined it, so it is reported as information rather than an error.
+	var offerRefusal: OfferRefusal? {
+		let haystack = technicalDetail.lowercased()
+		if haystack.contains("receiver-declined") || haystack.contains("declined-recently") {
+			return .declined
+		}
+		if haystack.contains("no-response") { return .noAnswer }
+		return nil
+	}
+
 	/// Prefers a `VnidropError` reason; else the localized description.
 	var technicalDetail: String {
 		if let vni = self as? VnidropError {