Spec v0.9.0 compliance

[toddbaert]

Tracks spec v0.9.0 compliance. Early stage; hook lifecycle + events are prerequisites for most items.

• Implement Hook interface #117 Implement Hooks #77 Implement Provider Hooks #78 Update Global API to manage hooks. #122 Wire hooks into evaluation

• Change path for gherkin tests #92 Pin gherkin harness to v0.9.0

• Events subsystem

• Tracking

• Logging hook

• Hook data (integrate existing type)

• Evaluation details in finally hook

• Telemetry utility (Appendix D)

• Isolated API instances

• Domain in provider init

• Provider state via events

• Multi-provider (optional)

• 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, provider status 2.8, Appendix E)