Captures the full librarian design (two-layer architecture, three-stage
pipeline, vendor-agnostic via LIBRARIAN_LLM env, propose-only / no
auto-apply) in docs/plans/librarian.md. Lands the first concrete Stage 1
piece: scripts/librarian_check_links.py, a lychee --offline wrapper
ported from ~/dev/coolrl/src/coolrl/dev/check_doc_links.py.
Also moves the librarian prompt from .claude/agents/ (Claude Code only)
to scripts/librarian-prompt.md so any CLI can load it as a system
prompt later. Fixes one stale README link the new checker caught:
docs/classic-port-notes.md → docs/archive/classic-port-notes.md.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>