The DuckDuckGo provider hit api.duckduckgo.com (the Instant Answer API),
which only serves Wikipedia / Wolfram-Alpha-style topics — empty
AbstractText / Results / RelatedTopics for the vast majority of agent
queries. The orchestrator then rejected the empty response and surfaced
'DuckDuckGo returned no renderable search content', leaving users with
no working free fallback.
Switch the provider to POST html.duckduckgo.com/html/ (the no-JS HTML
frontend) with a browser User-Agent, parse the result blocks (unwrapping
//duckduckgo.com/l/?uddg=… redirect URLs), and map recency to the df
form field (d/w/m/y). When DuckDuckGo serves the bot-detection modal
(HTTP 200/202 with anomaly-modal body) we surface a clear
SearchProviderError so the orchestrator can fall through to the next
provider with cause attached.
Fixes#3799
roboomp
755a61de07