feat: Initial library extraction from PIN LLM benchmark

DockerSandbox + LangChain file/shell tools extracted into a standalone package.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

docker_agent_sandbox/tools/copy_file.py

@@ -0,0 +1,37 @@
+"""copy_file.py – tool for copying files inside the sandbox."""
+
+from __future__ import annotations
+
+from shlex import quote
+from typing import TYPE_CHECKING
+
+from langchain_core.tools import BaseTool, tool
+from loguru import logger
+
+from docker_agent_sandbox.tools._utils import _parent
+
+if TYPE_CHECKING:
+    from docker_agent_sandbox.sandbox import DockerSandbox
+
+
+def make_copy_file_tool(sandbox: "DockerSandbox") -> BaseTool:
+    """Return a copy_file tool bound to *sandbox*."""
+
+    @tool
+    def copy_file(src: str, dst: str) -> str:
+        """
+        Copy a file from *src* to *dst*.
+
+        Parent directories of *dst* are created automatically.
+        Returns a confirmation message or an error.
+        """
+        logger.debug("Copying file inside sandbox: {!r} -> {!r}", src, dst)
+        mkdir_cmd = f"mkdir -p -- {quote(_parent(dst))}"
+        exit_code, output = sandbox.exec(
+            f"{mkdir_cmd} && cp -- {quote(src)} {quote(dst)}"
+        )
+        if exit_code != 0:
+            return f"[ERROR copying {src!r} to {dst!r}] {output.strip()}"
+        return f"[OK] Copied {src} -> {dst}"
+
+    return copy_file