Keep content containers that carry a data-date attribute

[Hor1zonZzz]

Fixes #441.

[data-date] removed any element with the attribute, including a post body wrapper (seen on a Ghost site with a custom theme), which left an empty article. The rule now skips elements that contain at least two paragraphs, following the existing header:not(:has(p + p)) rule. Date badges are still removed.

• New fixture selectors--data-date-content-container (anonymized): empty content before this change; four paragraphs after it, and its date badge is still removed.
• All existing fixtures are unchanged under linkedom and jsdom.

[Hor1zonZzz]

Repro with a live page and test runs, for review.

Live page: https://felixrieseberg.com/how-to-be-more-ambitious-a-tutorial-for-humans-with-models/ (Ghost theme, div.gh-content[data-date] wraps the body)

	words of Markdown
curl https://defuddle.md/<url>	frontmatter only, no body
npx defuddle@0.19.5 parse <url> --md	0 (No content could be extracted)
this branch: npm run build && node dist/cli.js parse <url> --md	2,202

The extra output after the fix is the article body only; no author box, navigation or player controls come back, since every other exact selector still applies.

Tests

Website dependencies were installed for both runs. Main was tested at 556d74e with a clean working tree using git stash push -u -m astra-baseline; the changes were restored afterward.

Command	main (556d74e)	This branch
npm test	FAIL: 824 passed, 2 failed; 44 test files passed, 1 failed	FAIL: 826 passed, 1 failed; 44 test files passed, 1 failed
npm run test:jsdom	FAIL: 824 passed, 2 failed; 44 test files passed, 1 failed	PASS: 827 tests, 45 test files
npm run lint:unused	PASS	PASS
npm run build	PASS (webpack bundle-size/performance warnings)	PASS (same webpack bundle-size/performance warnings)

The failures were 30-second timeouts in tests/x-article-surrogates.test.ts:

• Main, both test commands: repairs emoji split across bold span boundary and repairs emoji split across link boundary.
• This branch, npm test only: repairs emoji split across link boundary, also failing on main.

No new failures were observed. The differing timeout counts should not be interpreted as fixes from this selector change.

• tests/fixtures/selectors--data-date-content-container.html fails on main (empty content) and passes here.