chore: refresh browser extraction libraries

[steipete]

Summary

• update the browser content extractor from @mozilla/readability 0.4.4 to 0.6.0
• update Turndown from 7.1.2 to 7.2.4
• retain the existing GFM plugin and extraction behavior

Proof

• both pinned unpkg assets return HTTP 200
• existing-profile Chrome test loaded all three scripts, parsed Example Domain with Readability, and converted its article to Markdown with Turndown + GFM
• bun scripts/browser-tools.ts --help — success
• scripts/validate-skills — 49 skills validated
• autoreview (--mode local) — clean, no accepted/actionable findings

Existing gap

• the documented optional bun build ... --compile command still needs commander and puppeteer-core installed; this repo has no root dependency manifest today, independent of these two CDN pins