Fix basal pump units and Gym action-space limits

[LI-Jialu]

Summary

• convert basal requests from U/min to U/hour before applying the pump increment and limits
• expose basal limits in controller units (U/min) and use them in Gym and Gymnasium action spaces
• document the action units and add Insulet, Cozmo, Gym, and Gymnasium regression tests
• regenerate the deterministic trajectory fixture and its derived risk expectations

Rationale

pump_params.csv stores basal increments and limits in U/hour, while controller actions and the patient model use U/min. The previous implementation multiplied basal rates by the U-to-pmol conversion constant before applying the pump parameters, so realistic rates were effectively not quantized and the Gym upper bound was exposed as 30 U/min instead of 30 U/hour.

This addresses the basal/action-space portion of #71. Bolus behavior is intentionally unchanged because its interval/amount API semantics require a separate compatibility discussion. Patient equations, meals, rewards, and termination thresholds are unchanged.

Behavior impact

• Insulet maximum basal action: 0.5 U/min (30 U/hour)
• Cozmo maximum basal action: 35/60 U/min
• deterministic 48-hour adolescent#001 fixture: BG RMSE 0.87 mg/dL versus the old fixture, maximum absolute BG change 1.56 mg/dL, and 70-180 mg/dL TIR remains 100%

Testing

Ran the full unittest suite: 20 tests passed in 302.845 seconds.