Method RegisterAllAsync
RegisterAllAsync(CancellationToken)
Registers every content directory that exists: base first, then mods in dependency order so that a later mod overrides the ones it depends on. Returns how many registered, and logs the ones that exist but could not be registered (a name collision or a directory built for another build target) because those are silent content holes otherwise.
Zero is a legitimate answer, and it is the migration's switch: with nothing registered, AssetLibrary falls through to Addressables exactly as it did before the migration, which is what keeps the game playable while scopes are converted one at a time.
public static Task<int> RegisterAllAsync(CancellationToken ct = default)