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/title_config.py

@@ -0,0 +1,53 @@
+"""Configuration for automatic thread title generation."""
+
+from pydantic import BaseModel, Field
+
+
+class TitleConfig(BaseModel):
+    """Configuration for automatic thread title generation."""
+
+    enabled: bool = Field(
+        default=True,
+        description="Whether to enable automatic title generation",
+    )
+    max_words: int = Field(
+        default=6,
+        ge=1,
+        le=20,
+        description="Maximum number of words in the generated title",
+    )
+    max_chars: int = Field(
+        default=60,
+        ge=10,
+        le=200,
+        description="Maximum number of characters in the generated title",
+    )
+    model_name: str | None = Field(
+        default=None,
+        description="Model name to use for title generation (None = use default model)",
+    )
+    prompt_template: str = Field(
+        default=("Generate a concise title (max {max_words} words) for this conversation.\nUser: {user_msg}\nAssistant: {assistant_msg}\n\nReturn ONLY the title, no quotes, no explanation."),
+        description="Prompt template for title generation",
+    )
+
+
+# Global configuration instance
+_title_config: TitleConfig = TitleConfig()
+
+
+def get_title_config() -> TitleConfig:
+    """Get the current title configuration."""
+    return _title_config
+
+
+def set_title_config(config: TitleConfig) -> None:
+    """Set the title configuration."""
+    global _title_config
+    _title_config = config
+
+
+def load_title_config_from_dict(config_dict: dict) -> None:
+    """Load title configuration from a dictionary."""
+    global _title_config
+    _title_config = TitleConfig(**config_dict)