[feat] Support Proof-of-Work (PoW) challenges (Altcha, Friendly Captcha, and Wasm interstitials)

[nklowns]

Problem

Modern privacy-focused websites, public services, and search engines are increasingly moving away from traditional third-party image CAPTCHAs (reCAPTCHA, hCaptcha) toward Proof-of-Work (PoW) and WebAssembly-based challenges (such as Altcha, Friendly Captcha, mCaptcha, and Wasm-driven interstitials like Brave Search).

Currently, TRAWL has robust solvers for Cloudflare Turnstile, reCAPTCHA v2, hCaptcha, and GeeTest slide in packages/tiers/src/solvers/, but has no dedicated handler for PoW-based widgets or WebAssembly computation interstitials:

1. When a scraped form contains an Altcha or Friendly Captcha widget, solvePageCaptchas() does not identify or trigger the widget, preventing form submission.
2. When a site presents an interstitial Proof-of-Work challenge, short navigation timeouts can abort before the background WebAssembly / Web Worker finishes computing the solution nonce.

Proposed solution

Add native Proof-of-Work challenge support into TRAWL's architecture:

1. In-Page Widget Solvers (packages/tiers/src/solvers/):

   • Add altcha.ts to detect <altcha-widget> / .altcha elements and wait for the SHA-256 verification token.
   • Add friendlyCaptcha.ts to detect .frc-captcha widgets, trigger execution if interactive, and capture the solution token.
   • Register both in solvePageCaptchas() alongside existing Turnstile and reCAPTCHA solvers.

2. PoW / Wasm Interstitial Waiter (packages/tiers/src/utils/powWait.ts):

   • Add challenge detection for computational Wasm/PoW challenge gates in detect.ts.
   • Route through challengeRouter.ts with a dedicated waiter that monitors computation clearance cookies and redirects without premature timeouts.

Alternatives considered

• Relying solely on third-party solving APIs: Violates TRAWL's core philosophy of 100% local, free, zero-external-dependency solving.
• Handling PoW as generic timeouts: Causes non-deterministic failures when target sites adjust puzzle difficulty parameters.

Tier impact

• Fit inside an existing tier?
• Require a new tier or solver?
• Apply cross-cutting (caching, observability, config)?

Adds in-page solvers under packages/tiers/src/solvers/ and an interstitial waiter under packages/tiers/src/utils/ for Tier 3 browser execution.

Willingness to contribute

• I'd like to implement this myself and open a PR