Good basis (v2)

The reference basis $B$ (element numbers, e.g. 1,2,3) whose realization space chart is stored. The columns of $B$ are normalized to the identity. The choice of $B$ strongly affects how many variables and equations the chart has.

Bases are ranked by two integers computed from the fundamental bipartite graph of $B$ alone: a weighted count $H(B)$ of the genuine equations, and the exact number $\nu(B)$ of remaining coordinates. $H(B) = 0$ exactly when the chart is free. Charts are built for the few best-ranked bases, stopping at the first free one, and the simplest is kept.

Full details: docs/good_basis_v2.md.