refactor(Foundations): consolidate shared geometry and counting helpers - #1674

Node.js 20 is deprecated. The following actions target Node.js 20 but are being forced to run on Node.js 24: actions/checkout@v4. For more information see: https://github.blog/changelog/2025-09-19-deprecation-of-node-20-on-github-actions-runners/

Not declared at the PR head: `Orthogonal.cellPoint_disjoint`, `WordCount.card_filter_not_any`, `mem_occupiedCells`, `mem_retainedCells`, `boundary_eq`, `boundary_in_cell_box`, `access_inside_cell`, `ExactOneSAT.clauseY_bounds`, `ExactOneSAT.varX_bounds`, `Cslib.Logic.PL.ClauseSet.disjoint_flower_countingChild`, `Turing.MultiTapeTM.le_mul_succ`. Advisory only; see the job summary.