refactor(topology): Rename Wedge6 to Wedge, remove hardcoded node count

- Changed struct name from Wedge6 to Wedge
- Removed nnodes() method (node count now determined by basis)
- Updated all function signatures to use Wedge
- Added Wedge6 as backwards compatibility alias
- Added note explaining basis determines node count (P1=6, P2=15 nodes)

src/topology/wedge6.jl

@@ -2,9 +2,9 @@
 # License is MIT: see https://github.com/JuliaFEM/JuliaFEM.jl/blob/master/LICENSE
 
 """
-    Wedge6 <: AbstractTopology
+    Wedge <: AbstractTopology
 
-6-node linear prismatic/wedge element.
+Wedge/prism element topology (3D triangular extrusion).
 
 Reference element in 3D with triangular cross-section in (u,v) plane
 extruded along w direction from -1 to +1.
@@ -30,23 +30,29 @@ extruded along w direction from -1 to +1.
 
 Triangle base at w=-1, triangle top at w=+1.
 
+**Note:** Node count determined by basis function degree:
+- Lagrange{Wedge, 1}: 6 nodes (P1)
+- Lagrange{Wedge, 2}: 15 nodes (P2)
+
 **Zero allocation:** All functions return compile-time sized tuples.
 """
-struct Wedge6 <: AbstractTopology end
+struct Wedge <: AbstractTopology end
 
-nnodes(::Wedge6) = 6
-dim(::Wedge6) = 3
+dim(::Wedge) = 3
+
+# Backwards compatibility alias
+const Wedge6 = Wedge
 
 """
-    reference_coordinates(::Wedge6) -> NTuple{6, NTuple{3, Float64}}
+    reference_coordinates(::Wedge) -> NTuple{6, NTuple{3, Float64}}
 
-Reference coordinates for 6-node wedge:
+Reference coordinates for wedge vertices:
 - Bottom triangle (w=-1): (0,0,-1), (1,0,-1), (0,1,-1)
 - Top triangle (w=+1): (0,0,+1), (1,0,+1), (0,1,+1)
 
 **Zero allocation:** Returns tuple of tuples (stack allocated).
 """
-reference_coordinates(::Wedge6) = (
+reference_coordinates(::Wedge) = (
     (0.0, 0.0, -1.0), # N1
     (1.0, 0.0, -1.0), # N2
     (0.0, 1.0, -1.0), # N3
@@ -56,20 +62,20 @@ reference_coordinates(::Wedge6) = (
 )
 
 """
-    edges(::Wedge6) -> NTuple{9, Tuple{Int, Int}}
+    edges(::Wedge) -> NTuple{9, Tuple{Int, Int}}
 
 Edge connectivity for wedge (3 bottom + 3 top + 3 vertical = 9 edges).
 
 **Zero allocation:** Returns tuple of tuples (stack allocated).
 """
-edges(::Wedge6) = (
+edges(::Wedge) = (
     (1, 2), (2, 3), (3, 1),  # Bottom triangle
     (4, 5), (5, 6), (6, 4),  # Top triangle
     (1, 4), (2, 5), (3, 6),  # Vertical edges
 )
 
 """
-    faces(::Wedge6) -> NTuple{5, Tuple{Vararg{Int}}}
+    faces(::Wedge) -> NTuple{5, Tuple{Vararg{Int}}}
 
 Face connectivity for wedge:
 - 2 triangular faces (top and bottom)
@@ -77,7 +83,7 @@ Face connectivity for wedge:
 
 **Zero allocation:** Returns tuple of tuples (stack allocated).
 """
-faces(::Wedge6) = (
+faces(::Wedge) = (
     (1, 3, 2),    # Bottom triangle
     (4, 5, 6),    # Top triangle
     (1, 2, 5, 4), # Side quad