feat(fetchers): DuckDuckGo soft-block detection + link decoding (#26 #27)

[Liohtml]

Summary

New fetchers::search module for two DuckDuckGo HTML-endpoint quirks that silently break naive scrapers:

• DuckDuckGo HTML endpoint silently returns homepage (HTTP 202) when rate-limited — is_blocked() returns false #26 — is_duckduckgo_blocked(&Response): DuckDuckGo soft-blocks by returning HTTP 202 with its homepage instead of results. Since 202 is a success code, the generic Response::is_blocked() can't catch it. This helper detects it (202, or a 2xx DDG body with no result__a links). Kept separate from the generic is_blocked() so legitimate 202s from other hosts aren't misclassified.
• DuckDuckGo result links use redirect URLs (/l/?uddg=…) — actual target URL requires manual decoding #27 — decode_duckduckgo_href(&str): unwraps the //duckduckgo.com/l/?uddg=… redirect to the real percent-decoded target URL; non-DDG hrefs pass through unchanged.

README documents the limitation with a usage example and recommends Startpage / the Instant Answers API as more reliable.

Test plan

• 7 unit tests: redirect decode, pass-through (non-DDG + non-/l/), 202 block, homepage-without-results block, real-results not-blocked, non-DDG never blocked
• cargo test, clippy --all-targets -D warnings, fmt --check green

Closes #26
Closes #27

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Generated by Claude Code

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ℹ️ Review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro Plus

Run ID: 66e06496-50a9-447b-aae6-70b44447e07b

📥 Commits

Reviewing files that changed from the base of the PR and between 512a075 and 80b1a23.

📒 Files selected for processing (3)

• README.md
• src/fetchers/mod.rs
• src/fetchers/search.rs

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch claude/duckduckgo-helpers

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