TextForSpeech v0.15.0

What changed

replaced the raw persistenceURL: runtime initializer parameter with Runtime.PersistenceConfiguration, so callers now choose between .default and .file(url) through a small semantic API instead of passing a loosely shaped optional path
kept the resolved persistence path internal to Runtime, while preserving explicit caller control over file-backed storage when tests or host apps need it
changed the bundled default persistence namespace in debug builds to TextForSpeech-Debug, so debug app runs do not write into the bundled production TextForSpeech Application Support directory
updated the README, maintainer notes, and runtime tests to describe and verify the new persistence model

TextForSpeech.Runtime.init(..., persistenceURL:) has been replaced by TextForSpeech.Runtime.init(..., persistence:)

callers using the default runtime behavior do not need to pass anything; TextForSpeech.Runtime() still uses the default Application Support store
callers that previously passed persistenceURL: someURL should now pass persistence: .file(someURL)
bundled debug builds now use TextForSpeech-Debug by default, so existing debug-time persisted profile state under the bundled production namespace will not be read unless the caller explicitly points the runtime at that older file