feat(wsj): Add WSJ site adapters

[anyerqi]

Description

Adds WSJ adapters for use with bb-browser:

• wsj/headlines: reads latest headlines from NEXT_DATA.props.pageProps.latestHeadlines
• wsj/news: fetches a WSJ article by URL and extracts title, subtitle, authors, timestamps, and full article text
• wsj/frontpage: reads print edition front-page articles for a specified date from NEXT_DATA.props.pageProps.articles
• wsj/search: reads WSJ search results from NEXT_DATA.props.pageProps.searchResults

Testing

Tested locally with bb-browser site after copying the adapters into ~/.bb-browser/bb-sites/wsj:

  bb-browser site wsj/headlines --json
  bb-browser site wsj/search openai --json
  bb-browser site wsj/frontpage 20260428 --json
  bb-browser site wsj/news 'https://www.wsj.com/tech/ai/openai-misses-key-revenue-user-targets-in-high-stakes-sprint-toward-ipo-94a95273' --json

All four adapters returned structured JSON successfully.