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/sandbox/security.py

@@ -0,0 +1,45 @@
+"""Security helpers for sandbox capability gating."""
+
+from deerflow.config import get_app_config
+
+_LOCAL_SANDBOX_PROVIDER_MARKERS = (
+    "deerflow.sandbox.local:LocalSandboxProvider",
+    "deerflow.sandbox.local.local_sandbox_provider:LocalSandboxProvider",
+)
+
+LOCAL_HOST_BASH_DISABLED_MESSAGE = (
+    "Host bash execution is disabled for LocalSandboxProvider because it is not a secure "
+    "sandbox boundary. Switch to AioSandboxProvider for isolated bash access, or set "
+    "sandbox.allow_host_bash: true only in a fully trusted local environment."
+)
+
+LOCAL_BASH_SUBAGENT_DISABLED_MESSAGE = (
+    "Bash subagent is disabled for LocalSandboxProvider because host bash execution is not "
+    "a secure sandbox boundary. Switch to AioSandboxProvider for isolated bash access, or "
+    "set sandbox.allow_host_bash: true only in a fully trusted local environment."
+)
+
+
+def uses_local_sandbox_provider(config=None) -> bool:
+    """Return True when the active sandbox provider is the host-local provider."""
+    if config is None:
+        config = get_app_config()
+
+    sandbox_cfg = getattr(config, "sandbox", None)
+    sandbox_use = getattr(sandbox_cfg, "use", "")
+    if sandbox_use in _LOCAL_SANDBOX_PROVIDER_MARKERS:
+        return True
+    return sandbox_use.endswith(":LocalSandboxProvider") and "deerflow.sandbox.local" in sandbox_use
+
+
+def is_host_bash_allowed(config=None) -> bool:
+    """Return whether host bash execution is explicitly allowed."""
+    if config is None:
+        config = get_app_config()
+
+    sandbox_cfg = getattr(config, "sandbox", None)
+    if sandbox_cfg is None:
+        return False
+    if not uses_local_sandbox_provider(config):
+        return True
+    return bool(getattr(sandbox_cfg, "allow_host_bash", False))