fix: la Jacobi method failing (#202)

[ulises-jeremias]

la/jacobi_test.v is failing per issue #202. The Jacobi method appears to diverge or
not meet convergence criteria.

Task

1. Investigate the root cause — convergence criterion, diagonal dominance assumption, tolerance
2. Compare against matrix_ops solvers that work
3. Either fix the algorithm or add clear preconditions/warnings

Reference

• Issue: Jacobi method unsucessful #202

Files

• la/jacobi.v
• la/jacobi_test.v