Integrate smoothstate secondary Cox smoothing

[uriahf]

Draft integration of smoothstate into rtichoke_python for time-dependent calibration.

Current changes:

• add smoothstate>=0.1.0 as the intended runtime dependency;
• use the GitHub main branch as a temporary uv source until smoothstate 0.1.0 is published on PyPI;
• route the existing secondary-Cox calibration hook through smoothstate.smooth_state_cox();
• preserve rtichoke's existing Aalen-Johansen fallback behavior for degenerate/error cases;
• keep lifelines in the dev dependency group for equivalence testing only.

Before merge:

• run the existing calibration test suite and add a direct regression/equivalence test;
• benchmark the complete rtichoke secondary-Cox calibration call;
• publish smoothstate 0.1.0 to PyPI and remove the temporary [tool.uv.sources] Git override;
• remove the now-dead internal Cox/RCS implementation from calibration.py once equivalence is confirmed.

[github-actions]

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2026-08-19 08:15 UTC