Rename Barr-Houseman analytic module for 1996 reference

Rename analytic/barr_houseman.py to barr_houseman_96.py so the module path identifies the paper that supplies the closed-form Cartesian solution and cannot be confused with the related BH92 study. Update the package import and developer documentation, and add a focused assertion that uw.analytic.barr_houseman_96.FaultedMedium resolves to the registered public class.

Author: gthyagi

docs/developer/subsystems/analytic-solutions.md

@@ -511,13 +511,17 @@ the cost was imagined.
 
 ## A solution with a fault in it
 
-`FaultedMedium` (Barr & Houseman 1996, `analytic/barr_houseman.py`) is the linear
+`FaultedMedium` (Barr & Houseman 1996, `analytic/barr_houseman_96.py`) is the linear
 plane-strain case of their Appendix: a fault that terminates *inside* a viscous
 medium, on a disc of radius $R_0$ with the tip at the centre and the fault
 running out to the perimeter. It carries zero shear traction on the fault,
 continuous normal velocity and continuous normal stress across it, and slip
 $2U_0\sqrt{r/R_0}$.
 
+The year remains in the module name to distinguish this closed-form 1996
+solution from the related 1992 study, which does not provide the corresponding
+full Cartesian analytical field.
+
 It is here because it is the only absolute standard in the suite for a fault
 calculation. Everything else a fault model can be measured against is another
 discretisation.

src/underworld3/analytic/__init__.py

@@ -28,7 +28,7 @@
 
 from ._base import AnalyticSolution, FreeSlipWalls, FixedWalls
 
-from .barr_houseman import FaultedMedium
+from .barr_houseman_96 import FaultedMedium
 from .inclusion import EllipticalInclusion
 from .kramer import CylindricalStokes
 from .richards import GardnerSteady, GardnerTransient

src/underworld3/analytic/barr_houseman.py …underworld3/analytic/barr_houseman_96.pysrc/underworld3/analytic/barr_houseman.py renamed to src/underworld3/analytic/barr_houseman_96.py src/underworld3/analytic/barr_houseman.py renamed to src/underworld3/analytic/barr_houseman_96.py

@@ -453,6 +453,7 @@ def test_it_is_registered_in_the_family(mesh):
     assert uw.analytic.is_available("FaultedMedium")
     assert "Barr" in uw.analytic.describe("FaultedMedium")
 
+    assert uw.analytic.barr_houseman_96.FaultedMedium is uw.analytic.FaultedMedium
     assert uw.analytic.FaultedMedium.solves == "stokes"
     assert uw.analytic.FaultedMedium.symbolic is True
     assert uw.analytic.FaultedMedium.expensive_to_validate is False