small fixes

refactor: replace datetime.utcnow() with timezone-aware datetime.now(UTC)

feat(environment): add get_history() — returns copy of attack_history

feat(environment): add get_state() — synchronous EpisodeState snapshot

feat(environment): build and return StepResult with full observation

feat(environment): add termination logic — max_turns, attack_success, safety_flagged

feat(environment): append turn data to attack_history after each step

feat(environment): integrate reward_computer call in step() with mock fallback

feat(environment): integrate llm_pipeline call in step() with mock fallback

feat(environment): add conversation history builder from last 5 attack turns

feat(environment): add step() skeleton with active episode guard

feat(environment): call reward_computer.reset() in reset() to clear novelty scorer

feat(environment): implement reset() — zeros state and generates new episode_id

feat(environment): add set_llm_pipeline() injection method for Person 3

feat(environment): add set_reward_computer() injection method for Person 2

feat(environment): scaffold RedTeamEnvironment class with state fields