chore(test): delete legacy physics typing regression

Remove stale physics type tests superseded by tag-based traits.

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

test/physics/test_types.jl

@@ -1,66 +0,0 @@
-# This file is a part of JuliaFEM.
-# License is MIT: see https://github.com/JuliaFEM/JuliaFEM.jl/blob/master/LICENSE.md
-
-using Test
-using JuliaFEM
-
-@testset "Physics Category Types" begin
-    @testset "Elasticity{Dim}" begin
-        # Type construction
-        e2d = Elasticity{2}()
-        e3d = Elasticity{3}()
-
-        @test e2d isa Elasticity{2}
-        @test e3d isa Elasticity{3}
-        @test e2d isa AbstractPhysics
-        @test e3d isa AbstractPhysics
-
-        # Type stability
-        @test typeof(e2d) == Elasticity{2}
-        @test typeof(e3d) == Elasticity{3}
-    end
-
-    @testset "Thermal{Dim}" begin
-        # Type construction
-        thermal_2d = Thermal{2}()
-        thermal_3d = Thermal{3}()
-
-        @test thermal_2d isa Thermal{2}
-        @test thermal_3d isa Thermal{3}
-        @test thermal_2d isa AbstractPhysics
-        @test thermal_3d isa AbstractPhysics
-
-        # Type stability
-        @test typeof(thermal_2d) == Thermal{2}
-        @test typeof(thermal_3d) == Thermal{3}
-    end
-
-    @testset "required_field_type trait" begin
-        # Elasticity requires Displacement field
-        @test required_field_type(Elasticity{2}()) == Displacement{2}
-        @test required_field_type(Elasticity{3}()) == Displacement{3}
-
-        # Thermal requires Temperature field (dimension-independent)
-        @test required_field_type(Thermal{2}()) == Temperature
-        @test required_field_type(Thermal{3}()) == Temperature
-
-        # Type stability
-        @inferred required_field_type(Elasticity{3}())
-        @inferred required_field_type(Thermal{2}())
-        @inferred required_field_type(Thermal{3}())
-    end
-
-    @testset "Physics type dispatch" begin
-        # Different dimensions dispatch to different field types
-        function get_field_dim(physics::Elasticity{Dim}) where Dim
-            return Dim
-        end
-
-        @test get_field_dim(Elasticity{2}()) == 2
-        @test get_field_dim(Elasticity{3}()) == 3
-
-        # Thermal dimension parameter
-        @test required_field_type(Thermal{2}()) isa Type{Temperature}
-        @test required_field_type(Thermal{3}()) isa Type{Temperature}
-    end
-end