Fixes pages and page parts that 0.6.15 left white.

• Ordinary pages darken again. Sites that load bot-detection scripts or mention captchas were mistaken for "verify you are human" pages. Only markers on the challenge page itself count now.
• Site components darken again. Login and sign-up forms inside a "captcha" wrapper, and frames whose link mentions a challenge, are darkened. Real verification widgets (Turnstile, reCAPTCHA, hCaptcha, Arkose, GeeTest, HUMAN, AWS WAF, Friendly Captcha, DataDome, Kasada) are still left alone.
• Late-loading challenge pages are recognized once the page finishes loading, and a page is darkened after its challenge clears.

No new permissions.

Fixes Cloudflare Turnstile and other "verify you are human" checks failing while OLED Night is on. The experimental "reach inside locked web components" option no longer changes any page function; it now uses the extension API. Verification widgets and challenge pages from every provider (Turnstile, reCAPTCHA, hCaptcha, Arkose, DataDome, PerimeterX, GeeTest, AWS WAF and others) are always left untouched.