Revert "Revert direct attr access back to getattr (moving to separate PR)"

This reverts commit 73b5584.

Author: waltsims

kwave/solvers/cpp_simulation.py

@@ -39,7 +39,7 @@ def __init__(self, kgrid, medium, source, sensor, *, pml_size, pml_alpha, use_sg
 
         from kwave.solvers.validation import warn_cpp_alpha_mode_unsupported
 
-        warn_cpp_alpha_mode_unsupported(getattr(medium, "alpha_mode", None), stacklevel=3)
+        warn_cpp_alpha_mode_unsupported(medium.alpha_mode, stacklevel=3)
 
     def prepare(self, data_path=None):
         """Write HDF5 input file. Returns (input_file, output_file)."""

kwave/solvers/kspace_solver.py

@@ -411,7 +411,7 @@ def _setup_physics_operators(self):
 
         # Absorption/dispersion
         alpha_coeff_raw = getattr(self.medium, "alpha_coeff", 0)
-        alpha_mode = getattr(self.medium, "alpha_mode", None)
+        alpha_mode = self.medium.alpha_mode
         if not _is_enabled(alpha_coeff_raw):
             self._absorption = lambda div_u: 0
             self._dispersion = lambda rho: 0

kwave/solvers/validation.py

@@ -47,7 +47,7 @@ def validate_medium(medium, kgrid):
             power = float(np.asarray(medium.alpha_power).flat[0])
             if power < 0 or power > 3:
                 warnings.warn(f"medium.alpha_power={power} is outside typical range [0, 3].", stacklevel=3)
-            alpha_mode = getattr(medium, "alpha_mode", None)
+            alpha_mode = medium.alpha_mode
             if abs(power - 1.0) < 0.05 and alpha_mode != "no_dispersion":
                 raise ValueError(
                     f"medium.alpha_power={power} is too close to 1.0. The dispersion term "