test(opencti): add strong unit + integration tests for partial-state reliability

add deterministic unit tests covering failure at each critical stage (observable, report, external reference) to validate partial-state contract

enforce strict assertion on Created IDs message to guarantee no silent partial object leak

validate success path integrity and ensure no regression in return structure

verify organization and marking creation is executed only once per run (caching correctness)

add env-guarded live OpenCTI integration test for real API validation without breaking CI

This makes OpenCTI connector behavior testable, predictable and safe against API schema drift.

Author: gks281263