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/guardrails/provider.py

@@ -0,0 +1,56 @@
+"""GuardrailProvider protocol and data structures for pre-tool-call authorization."""
+
+from __future__ import annotations
+
+from dataclasses import dataclass, field
+from typing import Any, Protocol, runtime_checkable
+
+
+@dataclass
+class GuardrailRequest:
+    """Context passed to the provider for each tool call."""
+
+    tool_name: str
+    tool_input: dict[str, Any]
+    agent_id: str | None = None
+    thread_id: str | None = None
+    is_subagent: bool = False
+    timestamp: str = ""
+
+
+@dataclass
+class GuardrailReason:
+    """Structured reason for an allow/deny decision (OAP reason object)."""
+
+    code: str
+    message: str = ""
+
+
+@dataclass
+class GuardrailDecision:
+    """Provider's allow/deny verdict (aligned with OAP Decision object)."""
+
+    allow: bool
+    reasons: list[GuardrailReason] = field(default_factory=list)
+    policy_id: str | None = None
+    metadata: dict[str, Any] = field(default_factory=dict)
+
+
+@runtime_checkable
+class GuardrailProvider(Protocol):
+    """Contract for pluggable tool-call authorization.
+
+    Any class with these methods works - no base class required.
+    Providers are loaded by class path via resolve_variable(),
+    the same mechanism DeerFlow uses for models, tools, and sandbox.
+    """
+
+    name: str
+
+    def evaluate(self, request: GuardrailRequest) -> GuardrailDecision:
+        """Evaluate whether a tool call should proceed."""
+        ...
+
+    async def aevaluate(self, request: GuardrailRequest) -> GuardrailDecision:
+        """Async variant."""
+        ...