Third Stage 1 piece: scripts/librarian_check_oversize.py walks
non-archive markdown files and flags any over the 500-line soft cap
declared in AGENTS.md. Wired into scripts/librarian.sh.
Caught one real finding on first run: docs/performance.md at 914
lines. Splitting it into sub-topic notes is a separate cleanup task
— surfaced for the user, not auto-applied.
Updates docs/plans/librarian.md Progress + sets the next concrete
step to a stale-plan checker.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
