Comment out unreachable code paths in type stability helpers

- Line 69: else branch in _stabilize_mesh_type (map(identity, mesh))
- Line 125: non-concrete mesh warning in first MeshArray constructor
- Line 155: non-concrete mesh warning in second MeshArray constructor

These branches are unreachable in practice because typeof() always
returns the actual runtime type, which is concrete. The code is kept
as commented out for defensive programming and documentation purposes.

Reason: typeof(x) evaluates to the runtime type, not the compile-time
inferred type, so isconcretetype(typeof(x)) is always true.

Author: hsugawa8651

src/mesharrays/dense.jl

@@ -64,9 +64,11 @@ function _stabilize_mesh_type(mesh::Tuple)
     # Concretize the mesh tuple type
     if isconcretetype(typeof(mesh))
         return mesh
-    else
+    # else
+        # NOTE: This branch is unreachable in practice because typeof() always returns
+        # the actual runtime type, which is concrete. Kept for defensive programming.
         # Create a new tuple while preserving the type of each element
-        return map(identity, mesh)
+        # return map(identity, mesh)
     end
 end
 
@@ -121,9 +123,11 @@ function MeshArray(mesh...;
 
     mesh = _stabilize_mesh_type(mesh)
 
-    if isconcretetype(typeof(mesh)) == false
-        @warn "Mesh type $(typeof(mesh)) is not concrete, it may cause performance issue."
-    end
+    # NOTE: This check is unreachable in practice because typeof() always returns
+    # the actual runtime type, which is concrete. Kept for defensive programming.
+    # if isconcretetype(typeof(mesh)) == false
+    #     @warn "Mesh type $(typeof(mesh)) is not concrete, it may cause performance issue."
+    # end
 
     N = length(mesh)
     dims = tuple([length(v) for v in mesh]...)
@@ -151,9 +155,11 @@ function MeshArray(; mesh::Union{Tuple,AbstractVector},
 
     mesh = _stabilize_mesh_type(mesh)
 
-    if isconcretetype(typeof(mesh)) == false
-        @warn "Mesh type $(typeof(mesh)) is not concrete, it may cause performance issue."
-    end
+    # NOTE: This check is unreachable in practice because typeof() always returns
+    # the actual runtime type, which is concrete. Kept for defensive programming.
+    # if isconcretetype(typeof(mesh)) == false
+    #     @warn "Mesh type $(typeof(mesh)) is not concrete, it may cause performance issue."
+    # end
 
     @assert mesh isa Tuple "mesh should be a tuple, now get $(typeof(mesh))"
     N = length(mesh)