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.

backend/packages/harness/deerflow/security/html_cleaner.py

@@ -0,0 +1,63 @@
+"""HTML-to-text extraction with security-focused stripping."""
+
+from html.parser import HTMLParser
+from typing import Optional
+
+
+class SecureTextExtractor(HTMLParser):
+    """Extract visible text while stripping potentially dangerous elements.
+    
+    Based on OpenClaw's fetch.sh implementation.
+    """
+    
+    DANGEROUS_TAGS = {
+        'script', 'style', 'noscript', 
+        'header', 'footer', 'nav', 'aside',
+        'iframe', 'object', 'embed', 'form',
+    }
+    
+    def __init__(self):
+        super().__init__()
+        self.text = []
+        self.skip_depth = 0
+    
+    def handle_starttag(self, tag, attrs):
+        if tag in self.DANGEROUS_TAGS:
+            self.skip_depth += 1
+    
+    def handle_endtag(self, tag):
+        if tag in self.DANGEROUS_TAGS and self.skip_depth > 0:
+            self.skip_depth -= 1
+    
+    def handle_data(self, data):
+        if self.skip_depth == 0:
+            self.text.append(data)
+    
+    def get_text(self) -> str:
+        return ' '.join(self.text)
+
+
+def extract_secure_text(html: str, max_chars: Optional[int] = None) -> str:
+    """Extract clean text from HTML.
+    
+    Args:
+        html: Raw HTML content
+        max_chars: Optional maximum length
+        
+    Returns:
+        Clean text without dangerous elements
+    """
+    extractor = SecureTextExtractor()
+    extractor.feed(html)
+    text = extractor.get_text()
+    
+    # Collapse whitespace
+    import re
+    text = re.sub(r'[ \t]+', ' ', text)
+    text = re.sub(r'\n{3,}', '\n\n', text)
+    text = text.strip()
+    
+    if max_chars and len(text) > max_chars:
+        text = text[:max_chars-3] + '...'
+    
+    return text