gh-139580: Clarify pathlib full_match recursive pattern docs

[harjothkhara]

Closes gh-139580.

Summary

Clarify the PurePath.full_match() documentation for recursive ** patterns.
In particular, /a/** matches paths with a slash and following segment such as
/a/b, but not /a itself.

This is a docs-only fix matching the existing pathlib behavior. The blast radius
is limited to Doc/library/pathlib.rst; no runtime behavior changes are made.

Verification

Real behavior check:

./python.exe -c "from pathlib import Path; cases = ('/a', '/a/b', '/a/'); [print(f\"Path({case!r}) normalizes to {str(Path(case))!r}; full_match('/a/**') -> {Path(case).full_match('/a/**')}\") for case in cases]"

Output:

Path('/a') normalizes to '/a'; full_match('/a/**') -> False
Path('/a/b') normalizes to '/a/b'; full_match('/a/**') -> True
Path('/a/') normalizes to '/a'; full_match('/a/**') -> False

Docs checks:

make -C Doc html SOURCES=library/pathlib.rst SPHINXOPTS="-q"
make -C Doc doctest SOURCES=library/pathlib.rst SPHINXOPTS="-q"
git diff --check

Results:

• make -C Doc html SOURCES=library/pathlib.rst SPHINXOPTS="-q" passed.
• make -C Doc doctest SOURCES=library/pathlib.rst SPHINXOPTS="-q" passed.
• git diff --check passed.

[read-the-docs-community]

Documentation build overview

📚 cpython-previews | 🛠️ Build #33135752 | 📁 Comparing 303854b against main (a700732)

  🔍 Preview build  

1 file changed

± library/pathlib.html