chore(test): delete tetrahedron quadrature regression

Remove standalone tet quadrature tests superseded by unified rule checks.

- Drop `test/quadrature/test_tetrahedra.jl`.

test/quadrature/test_tetrahedra.jl

@@ -1,78 +0,0 @@
-# This file is a part of JuliaFEM.
-# License is MIT: see https://github.com/JuliaFEM/JuliaFEM.jl/blob/master/LICENSE.md
-
-@testset "Tetrahedron Quadrature Rules" begin
-
-    @testset "GaussLegendre{1} - 1 point (centroid)" begin
-        points = get_quadrature_points(Tetrahedron, GaussLegendre{1}())
-        @test length(points) == 1
-
-        # Check centroid location
-        @test points[1].coords[1] ≈ 1/4
-        @test points[1].coords[2] ≈ 1/4
-        @test points[1].coords[3] ≈ 1/4
-
-        # Check weight equals volume of reference tetrahedron (1/6)
-        @test points[1].weight ≈ 1/6
-    end
-
-    @testset "GaussLegendre{2} - 4 points" begin
-        points = get_quadrature_points(Tetrahedron, GaussLegendre{2}())
-        @test length(points) == 4
-
-        # Check weights sum to 1/6
-        weight_sum = sum(p.weight for p in points)
-        @test weight_sum ≈ 1/6
-
-        # Check all points are inside tetrahedron
-        for p in points
-            ξ, η, ζ = p.coords[1], p.coords[2], p.coords[3]
-            @test ξ >= 0 && η >= 0 && ζ >= 0
-            @test ξ + η + ζ <= 1
-        end
-
-        # All weights should be equal for this symmetric rule
-        @test all(p.weight ≈ points[1].weight for p in points)
-    end
-
-    @testset "GaussLegendre{3} - 5 points (has negative weight)" begin
-        points = get_quadrature_points(Tetrahedron, GaussLegendre{3}())
-        @test length(points) == 5
-
-        # Check weights sum to 1/6
-        weight_sum = sum(p.weight for p in points)
-        @test weight_sum ≈ 1/6
-
-        # This rule has one negative weight at centroid
-        @test any(p.weight < 0 for p in points)
-
-        # Centroid point should have negative weight
-        centroid_point = findfirst(p -> p.coords[1] ≈ 1/4 && p.coords[2] ≈ 1/4, points)
-        @test points[centroid_point].weight < 0
-    end
-
-    @testset "GaussLegendre{4} - 15 points" begin
-        points = get_quadrature_points(Tetrahedron, GaussLegendre{4}())
-        @test length(points) == 15
-
-        # Check weights sum to 1/6
-        weight_sum = sum(p.weight for p in points)
-        @test weight_sum ≈ 1/6 rtol=1e-10
-
-        # All weights should be positive
-        @test all(p.weight > 0 for p in points)
-
-        # Check all points are inside tetrahedron
-        for p in points
-            ξ, η, ζ = p.coords[1], p.coords[2], p.coords[3]
-            @test ξ >= 0 && η >= 0 && ζ >= 0
-            @test ξ + η + ζ <= 1 + 1e-10  # Small tolerance for rounding
-        end
-    end
-
-    @testset "Point coordinates are Vec type" begin
-        points = get_quadrature_points(Tetrahedron, GaussLegendre{2}())
-        @test points[1].coords isa Vec{3,Float64}
-        @test !(points[1].coords isa SVector)
-    end
-end