vectorize 2-D vfuncs in diffgeo and solver

[m-reuter]

Vectorize multi-function diffgeo operations and 2D Poisson solve

lapy/diffgeo.py

• Vectorized tria_compute_geodesic_f / compute_geodesic_f: gradient and divergence steps now operate on all input functions simultaneously; Poisson solve reduced to a single batched call
• Vectorized tria_compute_rotated_f / compute_rotated_f: added tn[:, np.newaxis, :] broadcasting in the np.cross rotation step; same batched Poisson solve

lapy/Solver.py

• Extended Solver.poisson() to accept a 2D right-hand side (n, k) in addition to 1D; 1D input is detected and output is squeezed back to 1D for full backward compatibility
• dvec and nvec sparse constraint vectors are tiled across all k columns via np.repeat
• Dirichlet/Neumann padding generalised to handle both 1D and 2D solution arrays

Tests

• Added vectorization tests into lapy/utils/tests/test_diffgeo.py (tria and tet gradient, divergence, geodesic_f, rotated_f multi-vs-single comparisons)
• Added Solver.poisson 2D rhs tests into lapy/utils/tests/test_solver.py
• Fixed test_smooth_laplace spurious DeprecationWarning by wrapping the deprecated smooth_vfunc call with pytest.warns(DeprecationWarning)

[codecov]

Codecov Report

❌ Patch coverage is 92.36111% with 11 lines in your changes missing coverage. Please review.
✅ Project coverage is 47.88%. Comparing base (83344c5) to head (8ecdfc4).
⚠️ Report is 6 commits behind head on main.

Files with missing lines	Patch %	Lines
lapy/diffgeo.py	95.20%	5 Missing and 1 partial ⚠️
lapy/solver.py	68.75%	2 Missing and 3 partials ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #109      +/-   ##
==========================================
+ Coverage   44.41%   47.88%   +3.47%     
==========================================
  Files          15       15              
  Lines        2758     2842      +84     
  Branches      348      359      +11     
==========================================
+ Hits         1225     1361     +136     
+ Misses       1411     1358      -53     
- Partials      122      123       +1     

Flag	Coverage Δ
unittests	47.88% <92.36%> (+3.47%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.