Extend doc for redefined-builtin

doc/data/messages/r/redefined-builtin/details.rst

@@ -0,0 +1,23 @@
+The `allowed-redefined-builtins <https://pylint.readthedocs.io/en/stable/user_guide/configuration/all-options.html#allowed-redefined-builtins>`_
+option lets you specify names that are permitted to shadow built-ins.
+
+However, this option is not effective for redefinitions at the module level or for global variables. For example:
+
+Module-Level Redefinitions::
+
+    # module_level_redefine.py
+    id = 1  # Shadows the built-in `id`
+
+Global Variable Redefinitions::
+
+    # global_variable_redefine.py
+    def my_func():
+        global len
+        len = 1  # Shadows the built-in `len`
+
+Rationale:
+
+Shadowing built-ins at the global scope is discouraged because it obscures their behavior
+throughout the entire module, increasing the risk of subtle bugs when the built-in is needed elsewhere.
+In contrast, local redefinitions are acceptable as their impact is confined to a specific scope,
+reducing unintended side effects and simplifying debugging.