ENH: Bump Eigen3 import tag to for/itk-20260430-fef1460e

Phase 2 prep for Eigen 5.x update. Points UpdateFromUpstream.sh at the
refreshed InsightSoftwareConsortium/eigen tag derived from gitlab
libeigen/eigen master tip fef1460 (2026-04-28), which provides Eigen
5.0.1.

Adds new top-level support headers introduced since the previous import:
AccelerateSupport, KLUSupport, ThreadPool, and Version. The Version header
is required because Eigen 5 moved EIGEN_{MAJOR,MINOR,PATCH}_VERSION out of
src/Core/util/Macros.h.

Author: hjmjohnson

Modules/ThirdParty/Eigen3/UpdateFromUpstream.sh

@@ -8,8 +8,9 @@ readonly name="Eigen3"
 readonly ownership="Eigen Upstream <kwrobot@kitware.com>"
 readonly subtree="Modules/ThirdParty/Eigen3/src/itkeigen"
 readonly repo="https://github.com/InsightSoftwareConsortium/eigen"
-readonly tag="for/itk-20260305-4c99fca"
+readonly tag="for/itk-20260430-fef1460ek"
 readonly paths="
+Eigen/AccelerateSupport
 Eigen/Cholesky
 Eigen/CholmodSupport
 Eigen/Core
@@ -20,6 +21,7 @@ Eigen/Geometry
 Eigen/Householder
 Eigen/IterativeLinearSolvers
 Eigen/Jacobi
+Eigen/KLUSupport
 Eigen/LU
 Eigen/MetisSupport
 Eigen/OrderingMethods
@@ -38,7 +40,9 @@ Eigen/StdDeque
 Eigen/StdList
 Eigen/StdVector
 Eigen/SuperLUSupport
+Eigen/ThreadPool
 Eigen/UmfPackSupport
+Eigen/Version
 Eigen/src
 
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