build: probe Eigen 3 and 5 separately in CMake config mode

Avoid relying on package-specific handling of a bounded version range when discovering Eigen through Eigen3Config.cmake.

Made-with: Cursor

Author: rwgk

tests/CMakeLists.txt

@@ -299,7 +299,10 @@ if(PYBIND11_TEST_FILES_EIGEN_I GREATER -1)
     set(EIGEN3_VERSION "${PYBIND11_EIGEN_VERSION_STRING}")
 
   else()
-    find_package(Eigen3 3.2.7...5 QUIET CONFIG)
+    find_package(Eigen3 3.2.7 QUIET CONFIG)
+    if(NOT Eigen3_FOUND)
+      find_package(Eigen3 5 QUIET CONFIG)
+    endif()
     set(EIGEN3_FOUND ${Eigen3_FOUND})
     set(EIGEN3_VERSION ${Eigen3_VERSION})