refactor: restructure repo layout

hooks/subagent-stop-log.sh

@@ -0,0 +1,6 @@
+#!/usr/bin/env bash
+# Observabilité : log chaque fin de subagent
+TIMESTAMP=$(date -u +"%Y-%m-%dT%H:%M:%SZ")
+PAYLOAD=$(cat)
+AGENT=$(echo "$PAYLOAD" | python3 -c "import json,sys; d=json.load(sys.stdin); print(d.get('agent_name','unknown'))" 2>/dev/null)
+echo "$TIMESTAMP agent=$AGENT" >> .claude/logs/subagent-decisions.log