Fix bug in simulation playback stopping early

[csmangum]

Fixes #11

Fix the simulation playback to continue until all available data points are visualized.

• visualization.py

  • Update _play_simulation method to ensure playback continues until the last step with data.
  • Update _step_to method to handle cases where steps are missing or incomplete.
  • Update _update_charts method to ensure playback reaches the end of the dataset.

• tests/test_simulation.py

  • Add a test to validate that the simulation playback continues until the last step with data.

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