feat(apple): saved devices and targeted transfers UI

Adds the native SwiftUI Saved Devices experience on top of the production
saved-device core, as a top-level destination in the iOS tab bar and the
macOS sidebar.

Core seam:
- App-facing saved-device domain models mirroring core/SavedDeviceModels.kt,
  with lifecycle helpers (canReceive/canResume/canCancel/canDelete) so views
  never hand-roll state checks.
- 21 gateway methods through CoreGateway/CoreRepository with UniFFI mapping.
  cancelTargetedTransfer, forgetSavedDevice and blockDevice run off the serial
  lane: each must reach the core while a targeted receive is blocking it.
- Payload-free pairingChanged/targetedTransferChanged signals, dispatched
  before the numeric-transferId guard since saved-device events identify
  their subject by peer endpoint or a string transfer id.

Experience:
- Screen lists saved devices and outstanding consent requests only; the
  global targeted-transfer history stays out, reachable per device.
- Details as a sheet with detents on compact layouts and a native inspector
  on macOS, owning Send, label, forget/block and that device's transfers.
- Label editing is transactional: the draft and editor survive a failed
  write, conflicting actions are refused while saving, and the editor closes
  only after the core confirms.
- Pairing and targeted-offer consent hosted at the app root, answerable from
  any tab and suppressed while a transfer approval is up. Dismissing a
  pairing prompt suppresses locally without consuming the single-use
  eligibility; dismissing an offer declines it, since an unanswered offer
  holds a slot in the core's bounded per-sender queue.
- Targeted send reuses the invitation composer's affordances with file,
  folder, rename, replace and cleanup parity. Picker copies are released on
  replace/remove/clear/cancel and after a successful create, but kept after a
  failure so retry does not require re-picking.
- Notifications for pairing requests and offers (withdrawn once answered) and
  for terminal targeted transfers. Wording follows direction: on the sending
  device the peer finished receiving, not us.

Localization:
- Widens 52 saved-device keys from kmp-only to both platforms.
- Five keys carried a literal %1$s with no declared args, which Compose
  renders positionally but the Apple generator emits as a plain constant,
  leaking the placeholder into the UI. They now use named args; Compose
  output is byte-identical.
- Adds targeted_offer_title/body. Reusing the invitation approval copy stated
  the roles backwards, announcing the sender as the receiver.

Also surfaces core startup failures: the startup overlay is drawn above the
snackbar host, so a failed initialize() was indistinguishable from an app
that never finished loading. AppModel now keeps the reason, logs it, and the
overlay shows it with a retry, plus the technical detail in DEBUG builds.

Send and receive between two devices is verified only partially; a missing
endpoint-identity credential currently blocks startup on the test device.

apple/Tests/Fakes.swift

@@ -81,6 +81,122 @@ final class FakeCoreGateway: CoreGateway {
 		return responseResult
 	}
 	func refresh() async -> Result<Void, Error> { .success(()) }
+
+	// MARK: - Saved devices
+
+	// Stubbed results
+	var savedDevices: [SavedDeviceModel] = []
+	/// Overrides `savedDevices` when set, so a test can fail one leg of the
+	/// five-read snapshot without stubbing the rest.
+	var savedDevicesResult: Result<[SavedDeviceModel], Error>?
+	var deviceRelationships: [DeviceRelationshipModel] = []
+	var pairingEligibilities: [PairingEligibilityModel] = []
+	var blockedDevices: [String] = []
+	var pendingTargetedOffers: [PendingTargetedOfferModel] = []
+	var targetedTransfers: [TargetedTransferModel] = []
+	var setLabelResult: Result<Void, Error> = .success(())
+	var forgetResult: Result<Void, Error> = .success(())
+	var blockResult: Result<Void, Error> = .success(())
+	var requestPairingResult: Result<Bool, Error> = .success(true)
+	var respondToPairingResult: Result<Bool, Error> = .success(true)
+	var offerResponseResult: Result<TargetedOfferResponseModel, Error> = .success(.declined)
+	var createTargetedTransferResult: Result<TargetedTransferModel, Error> = .failure(TestError.unimplemented)
+	var targetedReceiveResult: Result<Void, Error> = .success(())
+	var targetedCancelResult: Result<Void, Error> = .success(())
+	var targetedDeleteResult: Result<Void, Error> = .success(())
+
+	// Recorded calls
+	private(set) var setLabels: [(peerEndpointId: String, label: String?)] = []
+	private(set) var forgottenDevices: [String] = []
+	private(set) var blockedCalls: [String] = []
+	private(set) var unblockedCalls: [String] = []
+	private(set) var declinedEligibilities: [String] = []
+	private(set) var requestedPairings: [String] = []
+	private(set) var pairingResponses: [(peerEndpointId: String, accepted: Bool)] = []
+	private(set) var offerResponses: [(transferId: String, accepted: Bool)] = []
+	private(set) var createdTargetedTransfers: [(receiverEndpointId: String, sources: [ShareSource], transferName: String?)] = []
+	private(set) var targetedReceives: [(transferId: String, outputDirectoryUrl: String)] = []
+	private(set) var targetedResumes: [(id: String, outputDirectoryUrl: String)] = []
+	private(set) var cancelledTargetedTransfers: [String] = []
+	private(set) var deletedTargetedTransfers: [String] = []
+
+	func listPairingEligibilities() async -> Result<[PairingEligibilityModel], Error> {
+		.success(pairingEligibilities)
+	}
+	func declinePairingEligibility(peerEndpointId: String) async -> Result<Void, Error> {
+		declinedEligibilities.append(peerEndpointId)
+		return .success(())
+	}
+	func requestSavedDevicePairing(peerEndpointId: String) async -> Result<Bool, Error> {
+		requestedPairings.append(peerEndpointId)
+		return requestPairingResult
+	}
+	func respondToDevicePairing(peerEndpointId: String, accepted: Bool) async -> Result<Bool, Error> {
+		pairingResponses.append((peerEndpointId, accepted))
+		return respondToPairingResult
+	}
+	func listDeviceRelationships() async -> Result<[DeviceRelationshipModel], Error> {
+		.success(deviceRelationships)
+	}
+	func listSavedDevices() async -> Result<[SavedDeviceModel], Error> {
+		savedDevicesResult ?? .success(savedDevices)
+	}
+	func setSavedDeviceLabel(peerEndpointId: String, label: String?) async -> Result<Void, Error> {
+		setLabels.append((peerEndpointId, label))
+		return setLabelResult
+	}
+	func forgetSavedDevice(peerEndpointId: String) async -> Result<Void, Error> {
+		forgottenDevices.append(peerEndpointId)
+		return forgetResult
+	}
+	func blockDevice(peerEndpointId: String) async -> Result<Void, Error> {
+		blockedCalls.append(peerEndpointId)
+		return blockResult
+	}
+	func unblockDevice(peerEndpointId: String) async -> Result<Void, Error> {
+		unblockedCalls.append(peerEndpointId)
+		return .success(())
+	}
+	func listBlockedDevices() async -> Result<[String], Error> { .success(blockedDevices) }
+
+	// MARK: - Targeted transfers
+
+	func listPendingTargetedOffers() async -> Result<[PendingTargetedOfferModel], Error> {
+		.success(pendingTargetedOffers)
+	}
+	func respondToTargetedOffer(
+		transferId: String, accepted: Bool
+	) async -> Result<TargetedOfferResponseModel, Error> {
+		offerResponses.append((transferId, accepted))
+		return offerResponseResult
+	}
+	func createTargetedTransfer(
+		receiverEndpointId: String, sources: [ShareSource], transferName: String?
+	) async -> Result<TargetedTransferModel, Error> {
+		createdTargetedTransfers.append((receiverEndpointId, sources, transferName))
+		return createTargetedTransferResult
+	}
+	func listTargetedTransfers() async -> Result<[TargetedTransferModel], Error> {
+		.success(targetedTransfers)
+	}
+	func receiveTargetedTransfer(
+		transferId: String, outputDirectoryUrl: String
+	) async -> Result<Void, Error> {
+		targetedReceives.append((transferId, outputDirectoryUrl))
+		return targetedReceiveResult
+	}
+	func resumeTargetedTransfer(id: String, outputDirectoryUrl: String) async -> Result<Void, Error> {
+		targetedResumes.append((id, outputDirectoryUrl))
+		return targetedReceiveResult
+	}
+	func cancelTargetedTransfer(id: String) async -> Result<Void, Error> {
+		cancelledTargetedTransfers.append(id)
+		return targetedCancelResult
+	}
+	func deleteTargetedTransfer(id: String) async -> Result<Void, Error> {
+		deletedTargetedTransfers.append(id)
+		return targetedDeleteResult
+	}
 }
 
 /// Minimal `FileSystemService` fake — a writable path receive folder, no reveal.
@@ -103,6 +219,31 @@ final class FakeFileSystemService: FileSystemService {
 			[], transferName: transferName, senderName: senderName, accessPolicy: accessPolicy
 		)
 	}
+
+	/// Records targeted sends and forwards to the gateway so its recorders and
+	/// stubbed result drive the assertions.
+	private(set) var targetedSends: [(files: [PickedShareFile], transferName: String, receiver: String)] = []
+
+	func sendPickedFilesToSavedDevice(
+		repository: CoreGateway,
+		files: [PickedShareFile],
+		transferName: String,
+		receiverEndpointId: String
+	) async -> Result<TargetedTransferModel, Error> {
+		targetedSends.append((files, transferName, receiverEndpointId))
+		return await repository.createTargetedTransfer(
+			receiverEndpointId: receiverEndpointId,
+			sources: [],
+			transferName: transferName.isEmpty ? nil : transferName
+		)
+	}
+
+	/// Picker copies released via `discardPickedFiles`.
+	private(set) var discardedFiles: [String] = []
+
+	func discardPickedFiles(_ files: [PickedShareFile]) async {
+		discardedFiles.append(contentsOf: files.map(\.value))
+	}
 }
 
 @MainActor