Spec v0.9.0 compliance

Tracks [spec v0.9.0](https://github.com/open-feature/spec/releases/tag/v0.9.0) compliance.

- [ ] #384 Hook data ([spec 4.6](https://openfeature.dev/specification/sections/hooks))
- [ ] #518 Domain in provider init
- [ ] Bump `test-harness` submodule to v0.9.0

- [ ] Provider lifecycle event ownership (race-condition fix): add opt-in marker so providers emit their own `PROVIDER_READY`/`PROVIDER_ERROR`; SDK derives status from the provider event stream and keeps + deprecates the legacy synthetic path; update first-party providers ([spec 5.3.5](https://openfeature.dev/specification/sections/events#requirement-535), [provider status 2.8](https://openfeature.dev/specification/sections/providers#28-provider-status), [Appendix E](https://openfeature.dev/specification/appendix-e))

Start by reading the linked spec sections and the related issues #384 and #518, then inspect the test-harness submodule and first-party providers. Break the compliance work into the checklist items and verify completion against spec v0.9.0, including provider lifecycle event behavior and the updated harness.

Written by the indexing model from the issue text.