refactor(topology): Rename Pyr5 to Pyramid, remove hardcoded node count

- Changed struct name from Pyr5 to Pyramid
- Removed nnodes() method (node count now determined by basis)
- Updated all function signatures to use Pyramid
- Added Pyr5 as backwards compatibility alias
- Added note explaining basis determines node count (P1=5, P2=13, P3=29)

src/topology/pyr5.jl

@@ -2,9 +2,9 @@
 # License is MIT: see https://github.com/JuliaFEM/JuliaFEM.jl/blob/master/LICENSE
 
 """
-    Pyr5 <: AbstractTopology
+    Pyramid <: AbstractTopology
 
-5-node linear pyramid element.
+Pyramid element topology (3D mixed).
 
 Reference element in 3D parametric space with square base at z=-1
 and apex at (0,0,1).
@@ -27,23 +27,30 @@ Base nodes in [-1,1]² at z=-1, apex at (0,0,1).
 
 **Note:** This uses Code Aster convention (from lagrange_pyramids.jl).
 
+**Node count:** Determined by basis function degree:
+- Lagrange{Pyramid, 1}: 5 nodes
+- Lagrange{Pyramid, 2}: 13 nodes
+- Lagrange{Pyramid, 3}: 29 nodes
+
 **Zero allocation:** All functions return compile-time sized tuples.
 """
-struct Pyr5 <: AbstractTopology end
+struct Pyramid <: AbstractTopology end
 
-nnodes(::Pyr5) = 5
-dim(::Pyr5) = 3
+dim(::Pyramid) = 3
+
+# Backwards compatibility alias
+const Pyr5 = Pyramid
 
 """
-    reference_coordinates(::Pyr5) -> NTuple{5, NTuple{3, Float64}}
+    reference_coordinates(::Pyramid) -> NTuple{5, NTuple{3, Float64}}
 
-Reference coordinates for 5-node pyramid (Code Aster convention):
+Reference coordinates for pyramid (Code Aster convention):
 - Base nodes: (-1,-1,-1), (1,-1,-1), (1,1,-1), (-1,1,-1)
 - Apex: (0,0,1)
 
 **Zero allocation:** Returns tuple of tuples (stack allocated).
 """
-reference_coordinates(::Pyr5) = (
+reference_coordinates(::Pyramid) = (
     (-1.0, -1.0, -1.0), # N1
     (1.0, -1.0, -1.0), # N2
     (1.0, 1.0, -1.0), # N3
@@ -52,19 +59,19 @@ reference_coordinates(::Pyr5) = (
 )
 
 """
-    edges(::Pyr5) -> NTuple{8, Tuple{Int, Int}}
+    edges(::Pyramid) -> NTuple{8, Tuple{Int, Int}}
 
 Edge connectivity for pyramid (4 base edges + 4 edges to apex = 8 edges).
 
 **Zero allocation:** Returns tuple of tuples (stack allocated).
 """
-edges(::Pyr5) = (
+edges(::Pyramid) = (
     (1, 2), (2, 3), (3, 4), (4, 1),  # Base
     (1, 5), (2, 5), (3, 5), (4, 5),  # Edges to apex
 )
 
 """
-    faces(::Pyr5) -> NTuple{5, Tuple{Vararg{Int}}}
+    faces(::Pyramid) -> NTuple{5, Tuple{Vararg{Int}}}
 
 Face connectivity for pyramid:
 - 1 quadrilateral base
@@ -72,7 +79,7 @@ Face connectivity for pyramid:
 
 **Zero allocation:** Returns tuple of tuples (stack allocated).
 """
-faces(::Pyr5) = (
+faces(::Pyramid) = (
     (1, 4, 3, 2), # Base (quad)
     (1, 2, 5),    # Triangle
     (2, 3, 5),    # Triangle