Non-Asymptotically Valid and Asymptotically Exact (NAVAE) Confidence Intervals // Implements the non-asymptotically valid and asymptotically exact confidence intervals in two cases: estimation of the mean, and estimation of (a linear combination of) the coefficients in a linear regression model, following (Derumigny, Girard and Guyonvarch, 2025) doi:10.48550/arXiv.2507.16776.