feat: add shannon pentesting skill and AGPL-3.0 license

Copy the shannon skill from unicodeveloper/shannon into the Agent Skills
repo. Add proper full AGPL-3.0 license text to respect upstream licensing.
Update CLAUDE.md to document the new skill.

Co-Authored-By: Paperclip <noreply@paperclip.ing>

shannon/scripts/sync.sh

@@ -0,0 +1,31 @@
+#!/usr/bin/env bash
+# sync.sh - Deploy shannon skill to all host locations
+# Usage: bash scripts/sync.sh  (run from repo root)
+set -euo pipefail
+
+SRC="$(cd "$(dirname "$0")/.." && pwd)"
+echo "Source: $SRC"
+
+TARGETS=(
+  "$HOME/.claude/skills/shannon"
+  "$HOME/.agents/skills/shannon"
+  "$HOME/.codex/skills/shannon"
+)
+
+for t in "${TARGETS[@]}"; do
+  echo ""
+  echo "--- Syncing to $t ---"
+  mkdir -p "$t/scripts"
+
+  cp "$SRC/SKILL.md" "$t/"
+
+  # Helper scripts
+  if ls "$SRC/scripts/"*.sh &>/dev/null; then
+    rsync -a "$SRC/scripts/"*.sh "$t/scripts/"
+  fi
+
+  echo "  Deployed to $t"
+done
+
+echo ""
+echo "Sync complete."