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/config/tool_config.py

@@ -0,0 +1,20 @@
+from pydantic import BaseModel, ConfigDict, Field
+
+
+class ToolGroupConfig(BaseModel):
+    """Config section for a tool group"""
+
+    name: str = Field(..., description="Unique name for the tool group")
+    model_config = ConfigDict(extra="allow")
+
+
+class ToolConfig(BaseModel):
+    """Config section for a tool"""
+
+    name: str = Field(..., description="Unique name for the tool")
+    group: str = Field(..., description="Group name for the tool")
+    use: str = Field(
+        ...,
+        description="Variable name of the tool provider(e.g. deerflow.sandbox.tools:bash_tool)",
+    )
+    model_config = ConfigDict(extra="allow")