SwiftData Document-based app produces strange write errors

I have a document app built using SwiftData because frankly I'm too lazy to learn how to use FileDocument. The app's title is "Artsheets," and I'm using a document type that my app owns: com.wannafedor4.ArtsheetsDoc. The exported type identifier has these values:

• Description: Artsheets Document
• Identifier: com.wannafedor4.ArtsheetsDoc
• Conforms to: com.apple.package
• Reference URL: (none)
• Extensions: artsheets
• MIME Types: (none)

And the code:

• ArtsheetsApp.swift

import SwiftUI
import SwiftData

@main
struct ArtsheetsApp: App {
    var body: some Scene {
        DocumentGroup(editing: Sheet.self, contentType: .package) {
            EditorView()
        }
    }
}

• Document.swift

import SwiftUI
import SwiftData
import UniformTypeIdentifiers

@Model
final class Sheet {
    var titleKey: String
    @Relationship(deleteRule: .cascade) var columns: [Column]
    init(titleKey: String, columns: [Column]) {
        self.titleKey = titleKey
        self.columns = columns
    }
}

@Model
final class Column: Identifiable {
    var titlekey: String
    var text: [String]
    init(titlekey: String, text: [String]) {
        self.titlekey = titlekey
        self.text = text
    }
}

extension UTType {
    static var artsheetsDoc = UTType(exportedAs: "com.wannafedor4.artsheetsDoc")
}

I compiling for my iPhone 13 works, but then when creating a document I get this error:

Failed to create document. Error: Error Domain=com.apple.DocumentManager Code=2 "No location available to save “Untitled”." UserInfo={NSLocalizedDescription=No location available to save “Untitled”., NSLocalizedRecoverySuggestion=Enable at least one location to be able to save documents.}