feat(security): 新增工具沙箱安全机制

为所有工具插件添加沙箱拦截层，防止危险的文件访问、Shell命令和Python代码执行。
包含配置文件、核心校验逻辑及31个单元测试。

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

config/sandbox.yaml

@@ -0,0 +1,46 @@
+# KiloStar 沙箱安全策略配置
+sandbox:
+  enabled: true
+
+  # 文件系统沙箱
+  filesystem:
+    workspace_root: "/tmp/kilostar_workspace"
+    allowed_read_paths:
+      - "/tmp"
+    denied_paths:
+      - "/etc/shadow"
+      - "/etc/passwd"
+      - "/root"
+
+  # Shell 命令沙箱
+  shell:
+    enabled: true
+    blocked_commands:
+      - "rm -rf /"
+      - "mkfs"
+      - "dd "
+      - "shutdown"
+      - "reboot"
+    blocked_operators:
+      - "&&"
+      - "||"
+      - ";"
+      - "`"
+      - "$("
+    max_timeout: 60
+
+  # Python 执行器沙箱
+  python_executor:
+    enabled: true
+    max_timeout: 30
+    blocked_imports:
+      - "os"
+      - "subprocess"
+      - "shutil"
+      - "socket"
+      - "ctypes"
+    blocked_builtins:
+      - "exec"
+      - "eval"
+      - "compile"
+      - "__import__"