Anna's Archive and Waterstones now search by ISBN first and only fall
back to title/author when that comes back with an explicit no-results,
since a specific edition's ISBN can be unindexed even though the book
exists under another edition. Chez Mon Libraire is added as a third
source (isbn-based search, French no-results/found text patterns).
Results are cached per site+isbn via GM_getValue/GM_setValue for 14
days to cut down on repeat requests.
Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Shows Anna's Archive and Waterstones availability links when browsing
books on Bookshop.org, Amazon, or Waterstones. Includes @updateURL/
@downloadURL for Violentmonkey auto-update.
Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
