Replace the generic ScopedState (keyed by caller-provided root) with
InstanceState that hardcodes Instance.directory and integrates with
the instance dispose/reload lifecycle via a global task registry.
- Parallelize State + InstanceState disposal in reload/dispose
- Use Effect's Record.map and Struct.pick in auth-service
- Flatten nested Effect.gen in OAuth callback flow
- Add docstrings to ProviderAuthService interface
- Add State and InstanceState tests
Kit Langton