Add check-links.sh script for session-start URL verification

Checks all help resource URLs in checkApaFormatting.js in parallel and
reports any dead links via a systemMessage. Used by the local SessionStart
hook in .claude/settings.local.json (gitignored).

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: pfranktesting

scripts/check-links.sh

@@ -0,0 +1,38 @@
+#!/bin/bash
+# Check all help resource URLs in checkApaFormatting.js
+# Used by the SessionStart hook. Outputs JSON with systemMessage if any links fail.
+
+REPO_DIR="$(cd "$(dirname "$0")/.." && pwd)"
+JS_FILE="$REPO_DIR/src/checks/checkApaFormatting.js"
+
+[ -f "$JS_FILE" ] || exit 0
+
+# Extract https:// URLs from url: lines
+mapfile -t urls < <(grep -oP "url:\s*['\"]?\K(https://[^'\"]+)" "$JS_FILE" | sort -u)
+
+tmpdir=$(mktemp -d)
+
+for url in "${urls[@]}"; do
+  (
+    code=$(curl -s --head --connect-timeout 5 --max-time 8 -o /dev/null -w "%{http_code}" -L "$url" 2>/dev/null)
+    echo "$code $url" > "$tmpdir/$(echo -n "$url" | md5sum | cut -d' ' -f1).txt"
+  ) &
+done
+
+wait
+
+failed=()
+while IFS= read -r result_file; do
+  read -r code url < "$result_file"
+  # 200 OK, 301/302/303 redirects, 403 bot protection (Scribbr) = treat as live
+  if [[ ! "$code" =~ ^(200|301|302|303|403)$ ]]; then
+    failed+=("HTTP $code — $url")
+  fi
+done < <(find "$tmpdir" -name "*.txt")
+
+rm -rf "$tmpdir"
+
+if [ ${#failed[@]} -gt 0 ]; then
+  joined=$(printf '%s\\n' "${failed[@]}")
+  printf '{"systemMessage": "⚠️ APA Coach URL check: %d link(s) may be dead:\\n%s"}\n' "${#failed[@]}" "$joined"
+fi