Add HTTP mock tests for BitcoinTalk (fetchPage, Collect with server),
papers (IACR HTML parsing, arXiv XML parsing, PaperSourceAll), market
(historical with FromDate, invalid date, server errors), process
(ordered lists, blockquotes, h4-h6, nested objects, cancelled context),
excavate (resume skips completed, progress events), and state (copy
safety, cursor round-trip, null JSON).
Uses httptest.Server with rewriteTransport to intercept external HTTP
calls without touching the production code.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
b4e3d0555a