Create exported extractortest package with MockBrowser, MockDocument,
and MockNode that support selector-based responses for testing site
extractors without a real browser.
Add extraction tests for DuckDuckGo (result parsing, empty results, no
links, full search flow) and Powerball (drawing parsing, next drawing
parsing with billion/million, error cases, full GetCurrent flow).
Closes#21
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
