chore(test): delete triangle quadrature regression

Remove redundant triangle rule coverage.

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

test/quadrature/test_triangles.jl

@@ -1,106 +0,0 @@
-# This file is a part of JuliaFEM.
-# License is MIT: see https://github.com/JuliaFEM/JuliaFEM.jl/blob/master/LICENSE.md
-
-@testset "Triangle Quadrature Rules" begin
-
-    @testset "GaussLegendre{1} - 1 point" begin
-        points = get_quadrature_points(Triangle, GaussLegendre{1}())
-        @test length(points) == 1
-
-        # Check centroid location
-        @test points[1].coords[1] ≈ 1/3
-        @test points[1].coords[2] ≈ 1/3
-
-        # Check weight sums to area of reference triangle (0.5)
-        @test points[1].weight ≈ 0.5
-    end
-
-    @testset "GaussLegendre{2} - 3 points (default)" begin
-        points = get_quadrature_points(Triangle, GaussLegendre{2}())
-        @test length(points) == 3
-
-        # Check weights sum to 0.5
-        weight_sum = sum(p.weight for p in points)
-        @test weight_sum ≈ 0.5
-
-        # Check all points are inside triangle
-        for p in points
-            ξ, η = p.coords[1], p.coords[2]
-            @test ξ >= 0 && η >= 0 && ξ + η <= 1
-        end
-    end
-
-    @testset "GaussLegendre{2,:B} - 3 points (variant B)" begin
-        points = get_quadrature_points(Triangle, GaussLegendre{2,:B}())
-        @test length(points) == 3
-
-        # Check weights sum to 0.5
-        weight_sum = sum(p.weight for p in points)
-        @test weight_sum ≈ 0.5
-
-        # Variant B uses edge midpoints
-        @test any(p -> p.coords[1] ≈ 0.5 && p.coords[2] ≈ 0.0, points)
-        @test any(p -> p.coords[1] ≈ 0.0 && p.coords[2] ≈ 0.5, points)
-        @test any(p -> p.coords[1] ≈ 0.5 && p.coords[2] ≈ 0.5, points)
-    end
-
-    @testset "GaussLegendre{3} - 4 points (default)" begin
-        points = get_quadrature_points(Triangle, GaussLegendre{3}())
-        @test length(points) == 4
-
-        # Check weights sum to 0.5
-        weight_sum = sum(p.weight for p in points)
-        @test weight_sum ≈ 0.5
-
-        # All weights should be positive for default variant
-        @test all(p.weight > 0 for p in points)
-    end
-
-    @testset "GaussLegendre{3,:B} - 4 points (variant B, has negative weight)" begin
-        points = get_quadrature_points(Triangle, GaussLegendre{3,:B}())
-        @test length(points) == 4
-
-        # Check weights sum to 0.5
-        weight_sum = sum(p.weight for p in points)
-        @test weight_sum ≈ 0.5
-
-        # This variant has one negative weight
-        @test any(p.weight < 0 for p in points)
-    end
-
-    @testset "GaussLegendre{4} - 6 points" begin
-        points = get_quadrature_points(Triangle, GaussLegendre{4}())
-        @test length(points) == 6
-
-        # Check weights sum to 0.5
-        weight_sum = sum(p.weight for p in points)
-        @test weight_sum ≈ 0.5 rtol=1e-10
-    end
-
-    @testset "GaussLegendre{5} - 7 points" begin
-        points = get_quadrature_points(Triangle, GaussLegendre{5}())
-        @test length(points) == 7
-
-        # Check weights sum to 0.5
-        weight_sum = sum(p.weight for p in points)
-        @test weight_sum ≈ 0.5 rtol=1e-10
-
-        # Should include centroid point
-        @test any(p -> p.coords[1] ≈ 1/3 && p.coords[2] ≈ 1/3, points)
-    end
-
-    @testset "GaussLegendre{6} - 12 points" begin
-        points = get_quadrature_points(Triangle, GaussLegendre{6}())
-        @test length(points) == 12
-
-        # Check weights sum to 0.5
-        weight_sum = sum(p.weight for p in points)
-        @test weight_sum ≈ 0.5 rtol=1e-10
-    end
-
-    @testset "Point coordinates are Vec type" begin
-        points = get_quadrature_points(Triangle, GaussLegendre{2}())
-        @test points[1].coords isa Vec{2,Float64}
-        @test !(points[1].coords isa SVector)
-    end
-end