allow_fs_tools

Allowlist for FilesystemMiddleware's tools param, from --allow-fs-tools.

None means "all filesystem tools" and is also what --allow-fs-tools all parses to: it leaves the SDK's own default FilesystemMiddleware in place (no replacement). A list is an explicit allowlist of filesystem tool names, must include "read_file", and installs a restricted replacement (see create_cli_agent).