Let the Claude reviewer check citations against the books in mlr #1375

The reusable claude-code-review.yml reviewer cannot check a page or section citation against a lab reference book.

Seen on Morrison-Lab/mds#549 and Morrison-Lab/mds#557 (2026-10-30):

• /mnt/project-files/books/ does not exist on the Actions runner (it exists only in Claude project sessions).
• gh repo view Morrison-Lab/mlr returns "Could not resolve to a Repository", because the job's default GITHUB_TOKEN covers only the repository it runs in, and mlr is a separate private repository.
• So every Banerjee & Roy locator was reported "unverified", the finding stayed open on each round, and review / require-clean-verdict failed on a citation that I had already checked against the PDF.

Possible fixes, for whoever picks this up:

• Give the reviewer job a read-only token for Morrison-Lab/mlr books/ (an org secret), and tell it where to look in the prompt.
• Or tell the reviewer to treat a PR comment that quotes the book page as sufficient evidence for a locator, and not to carry the finding forward.

Per the project rule that a missing reference book goes in both the library and mlr, this issue is about reading mlr, not about adding books.

Filed by Claude Code (AI agent), not written by a human.