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/pyproject.toml

@@ -0,0 +1,47 @@
+[project]
+name = "deerflow-harness"
+version = "0.1.0"
+description = "DeerFlow agent harness framework"
+requires-python = ">=3.12"
+dependencies = [
+    "agent-client-protocol>=0.4.0",
+    "agent-sandbox>=0.0.19",
+    "dotenv>=0.9.9",
+    "exa-py>=1.0.0",
+    "httpx>=0.28.0",
+    "kubernetes>=30.0.0",
+    "langchain>=1.2.3",
+    "langchain-anthropic>=1.3.4",
+    "langchain-deepseek>=1.0.1",
+    "langchain-mcp-adapters>=0.1.0",
+    "langchain-openai>=1.1.7",
+    "langfuse>=3.4.1",
+    "langgraph>=1.0.6,<1.0.10",
+    "langgraph-api>=0.7.0,<0.8.0",
+    "langgraph-cli>=0.4.14",
+    "langgraph-runtime-inmem>=0.22.1",
+    "markdownify>=1.2.2",
+    "markitdown[all,xlsx]>=0.0.1a2",
+    "pydantic>=2.12.5",
+    "pyyaml>=6.0.3",
+    "readabilipy>=0.3.0",
+    "tavily-python>=0.7.17",
+    "firecrawl-py>=1.15.0",
+    "tiktoken>=0.8.0",
+    "ddgs>=9.10.0",
+    "duckdb>=1.4.4",
+    "langchain-google-genai>=4.2.1",
+    "langgraph-checkpoint-sqlite>=3.0.3",
+    "langgraph-sdk>=0.1.51",
+]
+
+[project.optional-dependencies]
+ollama = ["langchain-ollama>=0.3.0"]
+pymupdf = ["pymupdf4llm>=0.0.17"]
+
+[build-system]
+requires = ["hatchling"]
+build-backend = "hatchling.build"
+
+[tool.hatch.build.targets.wheel]
+packages = ["deerflow"]