fix(wikipedia): accept mobile (m.wikipedia.org) URLs

[GopalGB]

Summary

WikipediaConverter.accepts() rejected mobile Wikipedia URLs
(e.g. https://en.m.wikipedia.org/wiki/Foo) because its regex required
the language subdomain (2-3 letters) to be immediately followed by
.wikipedia.org. Mobile URLs have an extra .m segment between the
language code and .wikipedia.org, so they fell through to the
generic HtmlConverter, producing noisy navigation/footer markdown
instead of the clean main-content extraction WikipediaConverter
provides.

What changed

One-line regex change in _wikipedia_converter.py:

- if not re.search(r"^https?:\/\/[a-zA-Z]{2,3}\.wikipedia.org\/", url):
+ if not re.search(r"^https?:\/\/[a-zA-Z]{2,3}(\.m)?\.wikipedia.org\/", url):

The optional (\.m)? allows mobile subdomains while preserving:

• The ^https?: anchor
• Rejection of non-Wikipedia hosts like wikipedia.com
• Rejection of arbitrary subdomains like xyz.example.com

How to test

import re
pat = r"^https?:\/\/[a-zA-Z]{2,3}(\.m)?\.wikipedia.org\/"

# Should match
assert re.search(pat, "https://en.wikipedia.org/wiki/X")
assert re.search(pat, "https://en.m.wikipedia.org/wiki/X")
assert re.search(pat, "https://de.m.wikipedia.org/wiki/X")
assert re.search(pat, "https://fr.m.wikipedia.org/wiki/X")

# Should not match
assert not re.search(pat, "https://wikipedia.com/x")
assert not re.search(pat, "https://en.example.org/x")

Why this is small + safe

• Single line of production code changed
• The change is purely additive: every previously-accepted URL is still
  accepted (the new group (\.m)? is optional)
• No behavior change for the convert() path
• No new dependencies

Notes

This is orthogonal to PR #1723's hyphenated-language-code fix
(be-tarask, zh-classical, etc.) - mobile URLs are a separate gap
not covered by that PR's regex [a-zA-Z0-9-]+\.wikipedia.org because
the .m. segment still has to fit between the language code and
.wikipedia.org. The two fixes can compose if both are merged.

Co-Authored-By: Claude Opus 4.7 (1M context) noreply@anthropic.com

[GopalGB]

Friendly ping — license/cla is signed and the change is small (3-line URL parser tweak to accept m.wikipedia.org mobile URLs). Tests included. cc maintainers when cycles allow.