Add librarian Stage 1 orchestrator (scripts/librarian.sh)

Single entry point that runs every Stage 1 check in order and
aggregates exit codes — both checks always run so users see all
findings in one pass. Two checks wired up today (lychee link
integrity, file:line citations), more land incrementally as Stage 1
grows.

Removes scripts/librarian.sh from the ignore list now that the file
exists. Updates docs/plans/librarian.md Progress + Next Step.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

scripts/librarian.sh

@@ -0,0 +1,30 @@
+#!/usr/bin/env bash
+# Run all librarian Stage 1 checks. Exit code is non-zero if any check
+# failed; each check still runs even if a previous one failed, so users
+# see every finding in one pass.
+
+set -uo pipefail
+
+cd "$(dirname "$0")/.."
+
+overall=0
+
+echo "→ Markdown link integrity (lychee)"
+if ! uv run python scripts/librarian_check_links.py; then
+    overall=1
+fi
+echo
+
+echo "→ Code citations (file:line refs in inline code)"
+if ! uv run python scripts/librarian_check_citations.py; then
+    overall=1
+fi
+echo
+
+if [ "$overall" -eq 0 ]; then
+    echo "All Stage 1 checks passed."
+else
+    echo "One or more Stage 1 checks failed (see above)."
+fi
+
+exit "$overall"