Use this skill when the user says "clean librarian cache", "clear librarian cache", "clean up librarian repos", "prune librarian cache", "shrink librarian cache", "librarian is using too much space", "free up disk space from librarian", "how much space is librarian using", or wants to remove cached repositories that the librarian has cloned locally. Clears ~/.grimoire/librarian/cache/ to reclaim disk space without touching the curated library/ directory.