Summary by cubic

Introduce CodeAgentHistoryList to standardize CodeAgent history with a clear, typed, eval-compatible API. Replaces ad-hoc mocks and exposes history directly on NotebookSession.

• New Features

  • Added CodeAgentHistoryList with AgentHistoryList-compatible methods (final_result, is_done, errors, urls, screenshots, action_results, model_actions, save_to_file).
  • NotebookSession.history now returns CodeAgentHistoryList; session stores _complete_history and _usage_summary.
  • run() persists history and usage into the session for later access.

• Refactors

  • Removed DictToObject/MockAgentHistoryList; service.history now returns CodeAgentHistoryList.
  • Centralized history logic in views.py and simplified service.py.

^{Written for commit 9fe82f0. Summary will update automatically on new commits.}