gh-139580: Clarify pathlib full_match recursive pattern docs

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

Author: harjothkhara

Doc/library/pathlib.rst

@@ -575,6 +575,21 @@ Pure paths provide the following methods and properties:
       >>> PurePath('/a/b/c.py').full_match('**/*.py')
       True
 
+   A pattern ending with "``/**``" matches any path that begins with the
+   pattern's prefix followed by a separator.  For example "``/a/**``" matches
+   "``/a/b``" and "``/a/b/c``", but not "``/a``", because "``/a``" does not
+   begin with "``/a/``".  The recursive wildcard "``**``" can match zero
+   segments, but the separator before it must still be present in the path,
+   and :class:`PurePath` objects do not preserve trailing slashes (so
+   "``/a/``" is normalized to "``/a``")::
+
+      >>> PurePath('/a/b').full_match('/a/**')
+      True
+      >>> PurePath('/a').full_match('/a/**')
+      False
+      >>> PurePath('/a/').full_match('/a/**')
+      False
+
    .. seealso::
       :ref:`pathlib-pattern-language` documentation.