Initial commit: hardened DeerFlow factory

Vendored deer-flow upstream (bytedance/deer-flow) plus prompt-injection
hardening:

- New deerflow.security package: content_delimiter, html_cleaner,
  sanitizer (8 layers — invisible chars, control chars, symbols, NFC,
  PUA, tag chars, horizontal whitespace collapse with newline/tab
  preservation, length cap)
- New deerflow.community.searx package: web_search, web_fetch,
  image_search backed by a private SearX instance, every external
  string sanitized and wrapped in <<<EXTERNAL_UNTRUSTED_CONTENT>>>
  delimiters
- All native community web providers (ddg_search, tavily, exa,
  firecrawl, jina_ai, infoquest, image_search) replaced with hard-fail
  stubs that raise NativeWebToolDisabledError at import time, so a
  misconfigured tool.use path fails loud rather than silently falling
  back to unsanitized output
- Native client back-doors (jina_client.py, infoquest_client.py)
  stubbed too
- Native-tool tests quarantined under tests/_disabled_native/
  (collect_ignore_glob via local conftest.py)
- Sanitizer Layer 7 fix: only collapse horizontal whitespace, preserve
  newlines and tabs so list/table structure survives
- Hardened runtime config.yaml references only the searx-backed tools
- Factory overlay (backend/) kept in sync with deer-flow tree as a
  reference / source

See HARDENING.md for the full audit trail and verification steps.

deer-flow/backend/packages/harness/deerflow/mcp/client.py

@@ -0,0 +1,68 @@
+"""MCP client using langchain-mcp-adapters."""
+
+import logging
+from typing import Any
+
+from deerflow.config.extensions_config import ExtensionsConfig, McpServerConfig
+
+logger = logging.getLogger(__name__)
+
+
+def build_server_params(server_name: str, config: McpServerConfig) -> dict[str, Any]:
+    """Build server parameters for MultiServerMCPClient.
+
+    Args:
+        server_name: Name of the MCP server.
+        config: Configuration for the MCP server.
+
+    Returns:
+        Dictionary of server parameters for langchain-mcp-adapters.
+    """
+    transport_type = config.type or "stdio"
+    params: dict[str, Any] = {"transport": transport_type}
+
+    if transport_type == "stdio":
+        if not config.command:
+            raise ValueError(f"MCP server '{server_name}' with stdio transport requires 'command' field")
+        params["command"] = config.command
+        params["args"] = config.args
+        # Add environment variables if present
+        if config.env:
+            params["env"] = config.env
+    elif transport_type in ("sse", "http"):
+        if not config.url:
+            raise ValueError(f"MCP server '{server_name}' with {transport_type} transport requires 'url' field")
+        params["url"] = config.url
+        # Add headers if present
+        if config.headers:
+            params["headers"] = config.headers
+    else:
+        raise ValueError(f"MCP server '{server_name}' has unsupported transport type: {transport_type}")
+
+    return params
+
+
+def build_servers_config(extensions_config: ExtensionsConfig) -> dict[str, dict[str, Any]]:
+    """Build servers configuration for MultiServerMCPClient.
+
+    Args:
+        extensions_config: Extensions configuration containing all MCP servers.
+
+    Returns:
+        Dictionary mapping server names to their parameters.
+    """
+    enabled_servers = extensions_config.get_enabled_mcp_servers()
+
+    if not enabled_servers:
+        logger.info("No enabled MCP servers found")
+        return {}
+
+    servers_config = {}
+    for server_name, server_config in enabled_servers.items():
+        try:
+            servers_config[server_name] = build_server_params(server_name, server_config)
+            logger.info(f"Configured MCP server: {server_name}")
+        except Exception as e:
+            logger.error(f"Failed to configure MCP server '{server_name}': {e}")
+
+    return servers_config