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/skills/parser.py

@@ -0,0 +1,125 @@
+import logging
+import re
+from pathlib import Path
+
+from .types import Skill
+
+logger = logging.getLogger(__name__)
+
+
+def parse_skill_file(skill_file: Path, category: str, relative_path: Path | None = None) -> Skill | None:
+    """
+    Parse a SKILL.md file and extract metadata.
+
+    Args:
+        skill_file: Path to the SKILL.md file
+        category: Category of the skill ('public' or 'custom')
+
+    Returns:
+        Skill object if parsing succeeds, None otherwise
+    """
+    if not skill_file.exists() or skill_file.name != "SKILL.md":
+        return None
+
+    try:
+        content = skill_file.read_text(encoding="utf-8")
+
+        # Extract YAML front matter
+        # Pattern: ---\nkey: value\n---
+        front_matter_match = re.match(r"^---\s*\n(.*?)\n---\s*\n", content, re.DOTALL)
+
+        if not front_matter_match:
+            return None
+
+        front_matter = front_matter_match.group(1)
+
+        # Parse YAML front matter with basic multiline string support
+        metadata = {}
+        lines = front_matter.split("\n")
+        current_key = None
+        current_value = []
+        is_multiline = False
+        multiline_style = None
+        indent_level = None
+
+        for line in lines:
+            if is_multiline:
+                if not line.strip():
+                    current_value.append("")
+                    continue
+
+                current_indent = len(line) - len(line.lstrip())
+
+                if indent_level is None:
+                    if current_indent > 0:
+                        indent_level = current_indent
+                        current_value.append(line[indent_level:])
+                        continue
+                elif current_indent >= indent_level:
+                    current_value.append(line[indent_level:])
+                    continue
+
+            # If we reach here, it's either a new key or the end of multiline
+            if current_key and is_multiline:
+                if multiline_style == "|":
+                    metadata[current_key] = "\n".join(current_value).rstrip()
+                else:
+                    text = "\n".join(current_value).rstrip()
+                    # Replace single newlines with spaces for folded blocks
+                    metadata[current_key] = re.sub(r"(?<!\n)\n(?!\n)", " ", text)
+
+                current_key = None
+                current_value = []
+                is_multiline = False
+                multiline_style = None
+                indent_level = None
+
+            if not line.strip():
+                continue
+
+            if ":" in line:
+                # Handle nested dicts simply by ignoring indentation for now,
+                # or just extracting top-level keys
+                key, value = line.split(":", 1)
+                key = key.strip()
+                value = value.strip()
+
+                if value in (">", "|"):
+                    current_key = key
+                    is_multiline = True
+                    multiline_style = value
+                    current_value = []
+                    indent_level = None
+                else:
+                    metadata[key] = value
+
+        if current_key and is_multiline:
+            if multiline_style == "|":
+                metadata[current_key] = "\n".join(current_value).rstrip()
+            else:
+                text = "\n".join(current_value).rstrip()
+                metadata[current_key] = re.sub(r"(?<!\n)\n(?!\n)", " ", text)
+
+        # Extract required fields
+        name = metadata.get("name")
+        description = metadata.get("description")
+
+        if not name or not description:
+            return None
+
+        license_text = metadata.get("license")
+
+        return Skill(
+            name=name,
+            description=description,
+            license=license_text,
+            skill_dir=skill_file.parent,
+            skill_file=skill_file,
+            relative_path=relative_path or Path(skill_file.parent.name),
+            category=category,
+            enabled=True,  # Default to enabled, actual state comes from config file
+        )
+
+    except Exception as e:
+        logger.error("Error parsing skill file %s: %s", skill_file, e)
+        return None