feat(agents): Phase 7-10 hook system, plugins, skills, orchestration

Phase 7: Built-in Hooks (audit_log, dangerous_confirmation, security_scan)
Phase 8: Plugin system (PluginManager, PluginSandbox, PluginManifest)
Phase 9: Skills registry (SkillRegistry, local/plugin/MCP loaders)
Phase 10: TeamLeader, RemoteTransport, BackgroundTaskManager

backend/app/agents/tools/hooks/builtins/__init__.py

@@ -0,0 +1,11 @@
+"""内置 Hook 集合 - Phase 7"""
+
+from app.agents.tools.hooks.builtins.audit_log import AuditLogHook
+from app.agents.tools.hooks.builtins.dangerous_confirmation import DangerousConfirmationHook
+from app.agents.tools.hooks.builtins.security_scan import SecurityScanHook
+
+__all__ = [
+    "AuditLogHook",
+    "DangerousConfirmationHook",
+    "SecurityScanHook",
+]