Part1 Start Previews fail

1. Downloaded and unarchived Building a Great Mac App with SwiftUI
2. Set the team in Signing & Capabilities
3. Built project
4. Opened a view file with a preview provider -- e.g., GardenApp/Navigation/ContentView.swift
5. Pressed "Resume" in preview pane.

Result: "Cannot preview in this file -- Failed to launch Garden App.app"

Diagnostic dialog says:

FailedToLaunchError: Failed to launch Garden App.app

/Users/pf/Library/Developer/Xcode/DerivedData/Session1-epkltatcrbtmzhclsybsiwjohcvx/Build/Intermediates.noindex/Previews/Garden App Start/Products/Debug/Garden App.app

==================================

|  HumanReadableNSError: The operation couldn’t be completed. (OSStatus error -10825.)
|  
|  NSOSStatusErrorDomain (-10825):
|  ==_LSFunction: _LSOpenStuffCallLocal
|  ==_LSLine: 3762

Xcode: Version 13.0 beta (13A5154h) Big Sur: 11.4 (20F71)

Something's broken, but I don't know what. (Not a seasoned Xcode user.)