neuron: add latest patch release 8.2.6

Latest released version (8.2.6) was missing from the Spack build. Note that some dependencies needed to be pinned since NumPy 2 and Cython 3 came out in the meantime, and the 8.2 series is still not compatible with them.

packages/neuron/install-python-prefix-8.2.6.patch

+diff --git a/setup.py b/setup.py
+index 0ca138e60..bb85e416d 100644
+--- a/setup.py
++++ b/setup.py
+@@ -487,7 +487,7 @@ def setup_package():
+             extra_link_args=extra_link_args
+             + [
+                 "-Wl,-rpath,{}{}".format(
+-                    REL_RPATH, "/../../" if just_extensions else "/.data/lib/"
++                    REL_RPATH, "/../../../" if just_extensions else "/.data/lib/"
+                 )
+             ],
+             **extension_common_params,
+@@ -518,7 +518,7 @@ def setup_package():
+                 extra_compile_args=extra_compile_args
+                 + ["-O2" if "NRN_BUILD_FOR_UPLOAD" in os.environ else rx3d_opt_level],
+                 extra_link_args=extra_link_args
+-                + ["-Wl,-rpath,{}".format(REL_RPATH + "/../../.data/lib/")],
++                + ["-Wl,-rpath,{}".format(REL_RPATH + "/../../../../../../" if just_extensions else "/../../.data/lib/")],
+             )
+         )
+ 
+diff --git a/src/nrnpython/CMakeLists.txt b/src/nrnpython/CMakeLists.txt
+index 395c9e7d6..d62afce87 100644
+--- a/src/nrnpython/CMakeLists.txt
++++ b/src/nrnpython/CMakeLists.txt
+@@ -231,7 +231,10 @@ if(NRN_ENABLE_MODULE_INSTALL)
+   endforeach(pyexe)
+ 
+   add_dependencies(hoc_module nrniv_lib rxdmath ${nrnpython_lib_list})
+-  install(DIRECTORY ${NRN_PYTHON_BUILD_LIB} DESTINATION lib)
++  if(NOT DEFINED NRN_PYTHON_INSTALL_DIR)
++    set(NRN_PYTHON_INSTALL_DIR "lib")
++  endif()
++  install(DIRECTORY "${NRN_PYTHON_BUILD_LIB}/neuron" DESTINATION "${NRN_PYTHON_INSTALL_DIR}")
+ else()
+   # Make sure this is included in the wheels
+   install(FILES "${PROJECT_BINARY_DIR}/lib/python/neuron/_config_params.py"