test(combinatorial_maps): cover faces, dual, incidence, and validation

36 focused tests covering:
- face-orbit family completeness (every dart in exactly one face)
- Euler characteristic for the 4-cycle (sphere), minimal torus
  cellulation, tree, disconnected components, and isolated vertex
- orientable genus (sphere g=0, torus g=1, disconnected sum)
- orientation reversal: double-reversal identity, Euler/genus
  invariance, face bijection size
- connected components for single and disconnected maps
- dual: vertex count = face count, dual-of-dual vertex count,
  primal-to-dart bijection, torus dual
- vertex-face incidence multiplicity and boolean sets
- well-formedness validation: rotation length, involution,
  fixed-point-free reverse, foreign darts, vertex-count bound
- rotation successor cyclic behavior

Author: morluto