Searches BookOrbit's OPDS catalog for an issue's Standard edition and
extracts the book/file ids the web reader route needs. Hand-rolled Atom
parsing, no new dependencies; unit-tested against the real feed shape.
Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Va5eMEmWEnjMXBsBob5FDW
