fix: Correct error handling in hook evaluation and update artifact IDs

- Fix NPE in OpenFeatureClient.java where details.getErrorCode() was called before details object was built
- Use providerEval.getErrorCode() and providerEval.getErrorMessage() instead
- Refactor error handling to use immutable builder pattern consistently
- Update artifact IDs from openfeature-api/openfeature-sdk to api/sdk for cleaner naming
- All tests now pass including HookSpecTest

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <noreply@anthropic.com>

Author: aepfli