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>

kilostar/plugin/tool_plugin/search_file/__init__.py

@@ -36,21 +36,36 @@ async def search_file(
     Returns:
         匹配的文件名和行内容
     """
+    from kilostar.utils.sandbox import validate_path, PathViolation
+
     try:
-        cmd = (
-            f"grep -rn --include='{file_pattern}' "
-            f"-m {max_results} '{keyword}' '{directory}' 2>/dev/null "
-            f"| head -n {max_results}"
-        )
-        proc = await asyncio.create_subprocess_shell(
-            cmd,
+        directory = validate_path(directory, write=False)
+    except PathViolation as e:
+        return f"[Sandbox] {e}"
+
+    max_results = min(max_results, 100)
+
+    try:
+        grep_args = [
+            "grep", "-rn",
+            f"--include={file_pattern}",
+            "-m", str(max_results),
+            "--", keyword, directory,
+        ]
+        proc = await asyncio.create_subprocess_exec(
+            *grep_args,
             stdout=asyncio.subprocess.PIPE,
             stderr=asyncio.subprocess.PIPE,
         )
-        stdout, _ = await asyncio.wait_for(proc.communicate(), timeout=30)
+        stdout, _ = await asyncio.wait_for(
+            proc.communicate(), timeout=30
+        )
         output = stdout.decode("utf-8", errors="replace").strip()
         if not output:
             return f"未找到包含 '{keyword}' 的匹配项"
+        lines = output.split("\n")
+        if len(lines) > max_results:
+            output = "\n".join(lines[:max_results])
         return output
     except asyncio.TimeoutError:
         return "[Error] 搜索超时"