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/tests/test_config_version.py

@@ -0,0 +1,125 @@
+"""Tests for config version check and upgrade logic."""
+
+from __future__ import annotations
+
+import logging
+import tempfile
+from pathlib import Path
+
+import yaml
+
+from deerflow.config.app_config import AppConfig
+
+
+def _make_config_files(tmpdir: Path, user_config: dict, example_config: dict) -> Path:
+    """Write user config.yaml and config.example.yaml to a temp dir, return config path."""
+    config_path = tmpdir / "config.yaml"
+    example_path = tmpdir / "config.example.yaml"
+
+    # Minimal valid config needs sandbox
+    defaults = {
+        "sandbox": {"use": "deerflow.sandbox.local:LocalSandboxProvider"},
+    }
+    for cfg in (user_config, example_config):
+        for k, v in defaults.items():
+            cfg.setdefault(k, v)
+
+    with open(config_path, "w", encoding="utf-8") as f:
+        yaml.dump(user_config, f)
+    with open(example_path, "w", encoding="utf-8") as f:
+        yaml.dump(example_config, f)
+
+    return config_path
+
+
+def test_missing_version_treated_as_zero(caplog):
+    """Config without config_version should be treated as version 0."""
+    with tempfile.TemporaryDirectory() as tmpdir:
+        config_path = _make_config_files(
+            Path(tmpdir),
+            user_config={},  # no config_version
+            example_config={"config_version": 1},
+        )
+        with caplog.at_level(logging.WARNING, logger="deerflow.config.app_config"):
+            AppConfig._check_config_version(
+                {"sandbox": {"use": "deerflow.sandbox.local:LocalSandboxProvider"}},
+                config_path,
+            )
+        assert "outdated" in caplog.text
+        assert "version 0" in caplog.text
+        assert "version is 1" in caplog.text
+
+
+def test_matching_version_no_warning(caplog):
+    """Config with matching version should not emit a warning."""
+    with tempfile.TemporaryDirectory() as tmpdir:
+        config_path = _make_config_files(
+            Path(tmpdir),
+            user_config={"config_version": 1},
+            example_config={"config_version": 1},
+        )
+        with caplog.at_level(logging.WARNING, logger="deerflow.config.app_config"):
+            AppConfig._check_config_version(
+                {"config_version": 1},
+                config_path,
+            )
+        assert "outdated" not in caplog.text
+
+
+def test_outdated_version_emits_warning(caplog):
+    """Config with lower version should emit a warning."""
+    with tempfile.TemporaryDirectory() as tmpdir:
+        config_path = _make_config_files(
+            Path(tmpdir),
+            user_config={"config_version": 1},
+            example_config={"config_version": 2},
+        )
+        with caplog.at_level(logging.WARNING, logger="deerflow.config.app_config"):
+            AppConfig._check_config_version(
+                {"config_version": 1},
+                config_path,
+            )
+        assert "outdated" in caplog.text
+        assert "version 1" in caplog.text
+        assert "version is 2" in caplog.text
+
+
+def test_no_example_file_no_warning(caplog):
+    """If config.example.yaml doesn't exist, no warning should be emitted."""
+    with tempfile.TemporaryDirectory() as tmpdir:
+        config_path = Path(tmpdir) / "config.yaml"
+        with open(config_path, "w", encoding="utf-8") as f:
+            yaml.dump({"sandbox": {"use": "test"}}, f)
+        # No config.example.yaml created
+
+        with caplog.at_level(logging.WARNING, logger="deerflow.config.app_config"):
+            AppConfig._check_config_version({}, config_path)
+        assert "outdated" not in caplog.text
+
+
+def test_string_config_version_does_not_raise_type_error(caplog):
+    """config_version stored as a YAML string should not raise TypeError on comparison."""
+    with tempfile.TemporaryDirectory() as tmpdir:
+        config_path = _make_config_files(
+            Path(tmpdir),
+            user_config={"config_version": "1"},  # string, as YAML can produce
+            example_config={"config_version": 2},
+        )
+        # Must not raise TypeError: '<' not supported between instances of 'str' and 'int'
+        AppConfig._check_config_version({"config_version": "1"}, config_path)
+
+
+def test_newer_user_version_no_warning(caplog):
+    """If user has a newer version than example (edge case), no warning."""
+    with tempfile.TemporaryDirectory() as tmpdir:
+        config_path = _make_config_files(
+            Path(tmpdir),
+            user_config={"config_version": 3},
+            example_config={"config_version": 2},
+        )
+        with caplog.at_level(logging.WARNING, logger="deerflow.config.app_config"):
+            AppConfig._check_config_version(
+                {"config_version": 3},
+                config_path,
+            )
+        assert "outdated" not in caplog.text