AGS: Mac Steam games by Clifftop Games not detected when user selects .app file

[Thunderforge]

When a Mac user tries to add a LucasArts game on Steam, they can navigate to the .app file and ScummVM will detect the game. But when a Mac user tries to add an AGS game by Clifftop Games on Steam, navigating to the .app file results in ScummVM saying that no game can be found.

Expected Behavior

The user should be able to select the .app file for the Mac Steam version of the games from Clifftop Games, or any recognized game.

Current Behavior

ScummVM detects, for instance, The Fate of Atlantis.app but not KathyRain.app.

Reproduction

See also the attached animated GIF.

1. Launch a version of ScummVM that supports AGS games (tested with 5 May build)
2. Click "Add Game"
3. Navigate to ~/Library/Application Support/Steam/SteamApps/common

LucasArts game: Expected Behavior

1. Open the folder of a LucasArts game (such as Indiana Jones and the Fate of Atlantis), select the application within, and click the "Choose" button.
2. You will see that ScummVM recognizes the game.

Tested with Indiana Jones and the Fate of Atlants, Indiana Jones and the Last Crusade, Loom, and The Dig.

Clifftop Games game: Current Behavior

1. Open the folder of a Clifftop Games game (such as Kathy Rain), select the application within, and click the "Choose" button.
2. A dialog will appear saying "ScummVM could not find any game in the specified directory!"

Tested with Kathy Rain and Whispers of a Machine.

Clifftop Games game: Workaround

1. Open the folder of an AGS game (such as Kathy Rain), select the application within
2. Expand the "folder" of the application and navigate to Contents/Resources
3. Click the "Choose" button
4. The game is recognized by ScummVM

Thus the issue is not that ScummVM doesn't know about the game, it's that it doesn't treat the Mac Steam version of the game the same way as it does the Mac Steam versions of the LucasArts games.

(As an implementation issue: perhaps ScummVM should recognize that if this is a Mac and the "folder" ends in .app, then it should know to check for the existence of the necessary files in Contents/Resources before giving up).

[Thunderforge]

Animated GIF showing the issue. Two LucasArts Steam games are successfully detected, but Kathy Rain Steam is not