refactor(apple): make InvitationError typed and localize NFC prompts

Replace the free-form InvitationError.message(String) case with semantic
cases mapped to L10n keys at the UI boundary (Error.uiText), so user-facing
error text is localized instead of substring-matched from English blobs.
.raw(String) remains only for genuinely dynamic system/core messages.

Localize the CoreNFC alertMessage prompts via existing L10n keys, and add
SwiftLint rules (raw_alert_message, raw_invitation_error) to catch raw
alert strings and literal .raw("…") errors going forward.

apple/VniDrop/Platform/FileSystemService+iOS.swift

@@ -32,10 +32,10 @@ struct IosFileSystemService: FileSystemService {
 
 	func revealReceiveFolder(_ folder: ReceiveFolder) async -> Result<Void, Error> {
 		guard canRevealReceiveFolder(folder) else {
-			return .failure(InvitationError.message("The receive folder is not VniDrop Documents"))
+			return .failure(InvitationError.filesystemUnavailable)
 		}
 		guard let url = URL(string: "shareddocuments://\(folder.value)") else {
-			return .failure(InvitationError.message("The Files location URL is unavailable"))
+			return .failure(InvitationError.filesystemUnavailable)
 		}
 		let opened = await withCheckedContinuation { continuation in
 			DispatchQueue.main.async {
@@ -44,7 +44,7 @@ struct IosFileSystemService: FileSystemService {
 				}
 			}
 		}
-		return opened ? .success(()) : .failure(InvitationError.message("Could not open VniDrop Documents in Files"))
+		return opened ? .success(()) : .failure(InvitationError.filesystemUnavailable)
 	}
 
 	func discardPickedFiles(_ files: [PickedShareFile]) async {
@@ -62,7 +62,7 @@ struct IosFileSystemService: FileSystemService {
 		accessPolicy: ShareAccessPolicy
 	) async -> Result<Share, Error> {
 		guard !files.isEmpty else {
-			return .failure(InvitationError.message("Select at least one file to share"))
+			return .failure(InvitationError.shareEmpty)
 		}
 		let sources = files.map { $0.toIosShareSource() }
 		return await repository.shareSources(

apple/VniDrop/Platform/FileSystemService+macOS.swift

@@ -42,7 +42,7 @@ struct MacFileSystemService: FileSystemService {
 		accessPolicy: ShareAccessPolicy
 	) async -> Result<Share, Error> {
 		guard !files.isEmpty else {
-			return .failure(InvitationError.message("Select at least one file to share"))
+			return .failure(InvitationError.shareEmpty)
 		}
 		// Re-acquire security-scoped access to every picked source (from the bookmark
 		// captured at pick time) and hold it across the whole share call. The core

apple/VniDrop/Platform/ReceiveInvitationActions+iOS.swift

@@ -29,7 +29,7 @@ final class IosReceiveInvitationActions: NSObject, ReceiveInvitationActions, UID
 		picker.delegate = self
 		picker.modalPresentationStyle = .formSheet
 		guard let presenter = topPresenter() else {
-			return onResult(.failure(InvitationError.message("Could not find an iOS view controller")))
+			return onResult(.failure(InvitationError.viewControllerUnavailable))
 		}
 		presenter.present(picker, animated: true)
 	}
@@ -37,12 +37,12 @@ final class IosReceiveInvitationActions: NSObject, ReceiveInvitationActions, UID
 	func scanQrCode(onResult: @escaping (Result<String, Error>) -> Void) {
 		cancel()
 		guard let presenter = topPresenter() else {
-			return onResult(.failure(InvitationError.message("Could not find an iOS view controller")))
+			return onResult(.failure(InvitationError.viewControllerUnavailable))
 		}
 		ensureCameraAccess { [weak self] granted in
 			guard let self else { return }
 			guard granted else {
-				return onResult(.failure(InvitationError.message("Camera access is required to scan QR codes")))
+				return onResult(.failure(InvitationError.cameraUnavailable))
 			}
 			let scanner = QrScannerViewController { result in
 				self.qrController = nil
@@ -57,7 +57,7 @@ final class IosReceiveInvitationActions: NSObject, ReceiveInvitationActions, UID
 	func readNfcInvitation(onResult: @escaping (Result<String, Error>) -> Void) {
 		cancel()
 		guard NFCNDEFReaderSession.readingAvailable else {
-			return onResult(.failure(InvitationError.message("NFC reading is unavailable on this device")))
+			return onResult(.failure(InvitationError.nfcUnavailable))
 		}
 		let reader = InvitationNfcReader { [weak self] result in
 			self?.nfcReader = nil
@@ -80,7 +80,7 @@ final class IosReceiveInvitationActions: NSObject, ReceiveInvitationActions, UID
 		let result = documentResult
 		documentResult = nil
 		result?(Result {
-			guard let url = urls.first else { throw InvitationError.message("The selected invitation URL was invalid") }
+			guard let url = urls.first else { throw InvitationError.invalidInvitationURL }
 			let started = url.startAccessingSecurityScopedResource()
 			defer { if started { url.stopAccessingSecurityScopedResource() } }
 			let data = try Data(contentsOf: url)
@@ -157,19 +157,19 @@ final class QrScannerViewController: UIViewController, AVCaptureMetadataOutputOb
 	}
 
 	func cancelScan() {
-		finish(.failure(InvitationError.message("QR scanning was cancelled")))
+		finish(.failure(InvitationError.cancelled))
 	}
 
 	private func configureSession() {
 		guard let device = AVCaptureDevice.default(for: .video),
 			  let input = try? AVCaptureDeviceInput(device: device),
 			  session.canAddInput(input) else {
-			return finish(.failure(InvitationError.message("No camera is available")))
+			return finish(.failure(InvitationError.cameraUnavailable))
 		}
 		session.addInput(input)
 		let output = AVCaptureMetadataOutput()
 		guard session.canAddOutput(output) else {
-			return finish(.failure(InvitationError.message("Could not configure the QR scanner")))
+			return finish(.failure(InvitationError.cameraUnavailable))
 		}
 		session.addOutput(output)
 		output.setMetadataObjectsDelegate(self, queue: .main)
@@ -220,7 +220,7 @@ final class InvitationNfcReader: NSObject, NFCNDEFReaderSessionDelegate, @unchec
 
 	func start() {
 		let reader = NFCNDEFReaderSession(delegate: self, queue: .main, invalidateAfterFirstRead: true)
-		reader.alertMessage = "Hold your iPhone near a VniDrop invitation tag"
+		reader.alertMessage = String(localized: L10n.Receive.nfcWaiting)
 		session = reader
 		reader.begin()
 	}
@@ -233,7 +233,7 @@ final class InvitationNfcReader: NSObject, NFCNDEFReaderSessionDelegate, @unchec
 	func readerSession(_ session: NFCNDEFReaderSession, didInvalidateWithError error: Error) {
 		if finished { return }
 		let cancelled = (error as NSError).code == 200
-		finish(.failure(InvitationError.message(cancelled ? "NFC reading was cancelled" : error.localizedDescription)))
+		finish(.failure(cancelled ? InvitationError.cancelled : InvitationError.raw(error.localizedDescription)))
 	}
 
 	func readerSession(_ session: NFCNDEFReaderSession, didDetectNDEFs messages: [NFCNDEFMessage]) {
@@ -242,7 +242,7 @@ final class InvitationNfcReader: NSObject, NFCNDEFReaderSessionDelegate, @unchec
 				.flatMap { $0.records }
 				.compactMap { payloadAsInvitation($0) }
 				.first
-			guard let ticket else { throw InvitationError.message("This NFC tag does not contain a VniDrop invitation") }
+			guard let ticket else { throw InvitationError.nfcFailed }
 			return ticket
 		}
 		session.invalidate()

apple/VniDrop/Platform/ReceiveInvitationActions+macOS.swift

@@ -22,7 +22,7 @@ final class MacReceiveInvitationActions: ReceiveInvitationActions {
 		}
 		panel.begin { response in
 			guard response == .OK, let url = panel.url else {
-				onResult(.failure(InvitationError.message("cancelled")))
+				onResult(.failure(InvitationError.cancelled))
 				return
 			}
 			onResult(Result {
@@ -33,11 +33,11 @@ final class MacReceiveInvitationActions: ReceiveInvitationActions {
 	}
 
 	func scanQrCode(onResult: @escaping (Result<String, Error>) -> Void) {
-		onResult(.failure(InvitationError.message("QR scanning is unavailable on macOS")))
+		onResult(.failure(InvitationError.qrUnavailable))
 	}
 
 	func readNfcInvitation(onResult: @escaping (Result<String, Error>) -> Void) {
-		onResult(.failure(InvitationError.message("NFC is unavailable on macOS")))
+		onResult(.failure(InvitationError.nfcUnavailable))
 	}
 
 	func cancel() {}

apple/VniDrop/Platform/TransferShareActions+iOS.swift

@@ -36,7 +36,7 @@ final class IosTransferShareActions: NSObject, TransferShareActions {
 	func writeInvitationToNfc(ticket: String, onResult: @escaping (Result<Void, Error>) -> Void) {
 		cancelNfcWrite()
 		guard NFCNDEFReaderSession.readingAvailable else {
-			onResult(.failure(InvitationError.message("NFC is unavailable on this device")))
+			onResult(.failure(InvitationError.nfcUnavailable))
 			return
 		}
 		let writer = InvitationNfcWriter(ticket: ticket) { [weak self] result in
@@ -55,7 +55,7 @@ final class IosTransferShareActions: NSObject, TransferShareActions {
 	@MainActor
 	private func present(_ controller: UIViewController) throws {
 		guard let presenter = topPresenter() else {
-			throw InvitationError.message("Could not find an iOS view controller")
+			throw InvitationError.viewControllerUnavailable
 		}
 		presenter.present(controller, animated: true)
 	}
@@ -76,7 +76,7 @@ final class InvitationNfcWriter: NSObject, NFCNDEFReaderSessionDelegate, @unchec
 
 	func start() {
 		let reader = NFCNDEFReaderSession(delegate: self, queue: .main, invalidateAfterFirstRead: false)
-		reader.alertMessage = "Hold your iPhone near a writable NFC tag"
+		reader.alertMessage = String(localized: L10n.Transfer.nfcWaiting)
 		session = reader
 		reader.begin()
 	}
@@ -89,14 +89,14 @@ final class InvitationNfcWriter: NSObject, NFCNDEFReaderSessionDelegate, @unchec
 	func readerSession(_ session: NFCNDEFReaderSession, didInvalidateWithError error: Error) {
 		if finished { return }
 		let cancelled = (error as NSError).code == 200 // readerSessionInvalidationErrorUserCanceled
-		finish(.failure(InvitationError.message(cancelled ? "NFC writing was cancelled" : error.localizedDescription)))
+		finish(.failure(cancelled ? InvitationError.cancelled : InvitationError.raw(error.localizedDescription)))
 	}
 
 	func readerSession(_ session: NFCNDEFReaderSession, didDetectNDEFs messages: [NFCNDEFMessage]) {}
 
 	func readerSession(_ session: NFCNDEFReaderSession, didDetect tags: [NFCNDEFTag]) {
 		guard let firstTag = tags.first else {
-			return finish(.failure(InvitationError.message("No NFC tag was detected")))
+			return finish(.failure(InvitationError.nfcFailed))
 		}
 		// CoreNFC completion handlers run on the session's `.main` queue; these
 		// framework values are safe to use there.
@@ -109,18 +109,18 @@ final class InvitationNfcWriter: NSObject, NFCNDEFReaderSessionDelegate, @unchec
 				if let queryError { return self.finish(.failure(queryError)) }
 				switch status {
 				case .notSupported:
-					self.finish(.failure(InvitationError.message("This NFC tag does not support NDEF")))
+					self.finish(.failure(InvitationError.nfcFailed))
 				case .readOnly:
-					self.finish(.failure(InvitationError.message("This NFC tag is read-only")))
+					self.finish(.failure(InvitationError.nfcFailed))
 				default:
 					guard let message = self.invitationMessage() else {
-						return self.finish(.failure(InvitationError.message("Could not encode the invitation for NFC")))
+						return self.finish(.failure(InvitationError.nfcFailed))
 					}
 					tag.writeNDEF(message) { writeError in
 						if let writeError {
 							self.finish(.failure(writeError))
 						} else {
-							session.alertMessage = "Invitation written"
+							session.alertMessage = String(localized: L10n.Transfer.nfcWritten)
 							session.invalidate()
 							self.finish(.success(()))
 						}

apple/VniDrop/Platform/TransferShareActions+macOS.swift

@@ -17,7 +17,7 @@ final class MacTransferShareActions: TransferShareActions {
 		panel.allowedContentTypes = []
 		panel.begin { response in
 			guard response == .OK, let url = panel.url else {
-				onResult(.failure(InvitationError.message("cancelled")))
+				onResult(.failure(InvitationError.cancelled))
 				return
 			}
 			onResult(Result { try ticket.write(to: url, atomically: true, encoding: .utf8) })
@@ -28,7 +28,7 @@ final class MacTransferShareActions: TransferShareActions {
 		do {
 			let url = try writeTemporaryInvitation(ticket: ticket, transferName: transferName)
 			guard let view = NSApp.keyWindow?.contentView else {
-				onResult(.failure(InvitationError.message("No window available")))
+				onResult(.failure(InvitationError.noWindowAvailable))
 				return
 			}
 			let picker = NSSharingServicePicker(items: [url])
@@ -40,7 +40,7 @@ final class MacTransferShareActions: TransferShareActions {
 	}
 
 	func writeInvitationToNfc(ticket: String, onResult: @escaping (Result<Void, Error>) -> Void) {
-		onResult(.failure(InvitationError.message("NFC is unavailable on macOS")))
+		onResult(.failure(InvitationError.nfcUnavailable))
 	}
 
 	func cancelNfcWrite() {}