Basis regression files used to `include` topology and generated basis sources
directly from `../../src`, which drifted from package exports and hid missing
wiring until CI.
- Replace the relative `include` chain with `using JuliaFEM` so tests hit the
real module surface (`Lagrange{P}`, parametrized topologies, generated tables).
Import `JuliaFEM` in the topic runner and include new Piola/Nedelec,
integration-basis quadrature, and basis-description regressions.
- Reorder derivative/type-stability includes after adding coverage files.
Test suite organizer for basis module.
Includes all basis function tests: partition of unity, derivatives,
interpolation, type stability, numerical accuracy, etc.
New 31-line test for partition of unity property:
- Tests that sum of basis functions equals 1.0
- Covers Seg2, Tri3, Quad4 elements
- Included in test/basis/runtests.jl
- Validates fundamental basis function property
Ensures basis functions satisfy partition of unity requirement.