Request Search Assist explicitly instead of relying on automatic display

[variablenix]

Summary

Request Search Assist explicitly using assiston=1, the destination of DuckDuckGo's official !assist bang, instead of relying on the normal search page to choose to show an answer.

• Use the explicit route in both lightweight and rendered-browser requests.
• Include it in no-answer links and uncited Search Assist fallback links.
• Preserve the question with URL encoding, including punctuation, Unicode, and query-parameter-like input.
• Document that this is a web route, not a public API or a challenge bypass.

Source: https://duckduckgo.com/bang.js (assist entry).

Verification

• go test -race ./...
• go vet ./...
• git diff --check
• Regression test checks that original and normalized retry requests both explicitly request Search Assist.
• Live server tests passed for the cost comparison and existing definition/question smoke cases.

Search Assist availability remains provider-controlled. This does not guarantee answers for every query or override anti-automation challenges.