Simplified process startup on macOS and Linux

Apple/Shared/Constants.swift

@@ -0,0 +1,22 @@
+@_implementationOnly import Constants
+
+public enum Constants {
+    enum Error: Swift.Error {
+        case invalidAppGroupIdentifier
+    }
+
+    public static let bundleIdentifier = AppBundleIdentifier
+    public static let appGroupIdentifier = AppGroupIdentifier
+
+    public static var groupContainerURL: URL {
+        get throws { try _groupContainerURL.get() }
+    }
+
+    private static let _groupContainerURL: Result<URL, Error> = {
+        guard let groupContainerURL = FileManager.default
+            .containerURL(forSecurityApplicationGroupIdentifier: appGroupIdentifier) else {
+            return .failure(.invalidAppGroupIdentifier)
+        }
+        return .success(groupContainerURL)
+    }()
+}