defaultTickIdentifier

The tick identifier BackgroundTaskManager.shared uses when the app never called create: the main bundle identifier plus .backgrounder-tick (e.g. dev.example.app.backgrounder-tick). It must appear in BGTaskSchedulerPermittedIdentifiers; the Gradle plugin adds it when backgrounder.iosBundleIdentifier is set. Exposed so apps that maintain the plist by hand can read the exact string.

@OptIn(ExperimentalObjCName::class): Swift-rename annotation; stable in practice and required by SKIE (CLAUDE.md §8).