chore(test): remove physics validation experiment

Delete unmaintained validation harness for retired Physics workflows.

- Drop `test/physics/test_validation.jl`.

test/physics/test_validation.jl

@@ -1,149 +0,0 @@
-# This file is a part of JuliaFEM.
-# License is MIT: see https://github.com/JuliaFEM/JuliaFEM.jl/blob/master/LICENSE.md
-
-"""
-Validation tests for Physics types.
-
-Tests error handling and edge cases.
-"""
-
-using Test
-using JuliaFEM
-using Tensors
-
-@testset "Physics Validation" begin
-    # Helper to create minimal mesh
-    function create_test_mesh()
-        nodes = Vec{3,Float64}[
-            Vec{3}((0.0, 0.0, 0.0)),
-            Vec{3}((1.0, 0.0, 0.0)),
-            Vec{3}((1.0, 1.0, 0.0)),
-            Vec{3}((0.0, 1.0, 0.0)),
-            Vec{3}((0.0, 0.0, 1.0)),
-            Vec{3}((1.0, 0.0, 1.0)),
-            Vec{3}((1.0, 1.0, 1.0)),
-            Vec{3}((0.0, 1.0, 1.0))
-        ]
-        connectivity = [NTuple{8,UInt32}((1, 2, 3, 4, 5, 6, 7, 8))]
-        element_sets = Dict{Symbol,Set{UInt32}}(:all => Set(UInt32(1)), :solid => Set(UInt32(1)))
-        return Mesh{8,Hexahedron{8}}(nodes, connectivity, element_sets)
-    end
-
-    @testset "Physics mesh reference (not copy)" begin
-        mesh = create_test_mesh()
-        material = LinearElastic(E=210e9, ν=0.3)
-
-        physics1 = Physics(
-            name="physics1",
-            mesh=mesh,
-            element_set=:all,
-            field=Displacement{3}(),
-            formulation=ContinuumFormulation{FullThreeD}(),
-            material=material
-        )
-
-        physics2 = Physics(
-            name="physics2",
-            mesh=mesh,
-            element_set=:solid,
-            field=Displacement{3}(),
-            formulation=ContinuumFormulation{FullThreeD}(),
-            material=material
-        )
-
-        # Both physics reference the SAME mesh object
-        @test physics1.mesh === mesh
-        @test physics2.mesh === mesh
-        @test physics1.mesh === physics2.mesh
-    end
-
-    @testset "Type parameter specialization" begin
-        mesh = create_test_mesh()
-        material = LinearElastic(E=210e9, ν=0.3)
-
-        # 3D displacement
-        physics_3d = Physics(
-            name="3d",
-            mesh=mesh,
-            element_set=:all,
-            field=Displacement{3}(),
-            formulation=ContinuumFormulation{FullThreeD}(),
-            material=material
-        )
-
-        # Verify type parameters can be used for dispatch
-        @test physics_3d isa Physics{
-            ContinuumFormulation{FullThreeD},
-            Displacement{3},
-            Mesh{8,Hexahedron{8}},
-            LinearElastic
-        }
-
-        # Type is fully concrete
-        @test isconcretetype(typeof(physics_3d))
-    end
-
-    @testset "Multiple materials with same mesh" begin
-        mesh = create_test_mesh()
-
-        material1 = LinearElastic(E=210e9, ν=0.3)
-        material2 = LinearElastic(E=70e9, ν=0.33)  # Aluminum
-
-        physics1 = Physics(
-            name="steel",
-            mesh=mesh,
-            element_set=:all,
-            field=Displacement{3}(),
-            formulation=ContinuumFormulation{FullThreeD}(),
-            material=material1
-        )
-
-        physics2 = Physics(
-            name="aluminum",
-            mesh=mesh,
-            element_set=:all,
-            field=Displacement{3}(),
-            formulation=ContinuumFormulation{FullThreeD}(),
-            material=material2
-        )
-
-        # Same mesh, different materials
-        @test physics1.mesh === physics2.mesh
-        @test physics1.material !== physics2.material
-        @test physics1.material.E ≈ 210e9
-        @test physics2.material.E ≈ 70e9
-    end
-
-    @testset "Boundary conditions independence" begin
-        mesh = create_test_mesh()
-        material = LinearElastic(E=210e9, ν=0.3)
-
-        physics1 = Physics(
-            name="p1",
-            mesh=mesh,
-            element_set=:all,
-            field=Displacement{3}(),
-            formulation=ContinuumFormulation{FullThreeD}(),
-            material=material
-        )
-
-        physics2 = Physics(
-            name="p2",
-            mesh=mesh,
-            element_set=:all,
-            field=Displacement{3}(),
-            formulation=ContinuumFormulation{FullThreeD}(),
-            material=material
-        )
-
-        # Add BCs to physics1
-        add_dirichlet!(physics1, [1, 2], [1, 2, 3], 0.0)
-        add_neumann!(physics2, [7, 8], Vec{3}((0.0, -1000.0, 0.0)))
-
-        # BCs are independent
-        @test length(physics1.bc_dirichlet.node_ids) == 2
-        @test length(physics2.bc_dirichlet.node_ids) == 0
-        @test length(physics1.bc_neumann.surface_ids) == 0
-        @test length(physics2.bc_neumann.surface_ids) == 2
-    end
-end