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/scripts/wizard/steps/search.py

@@ -0,0 +1,66 @@
+"""Step: Web search configuration."""
+
+from __future__ import annotations
+
+from dataclasses import dataclass
+
+from wizard.providers import SEARCH_PROVIDERS, WEB_FETCH_PROVIDERS, SearchProvider, WebProvider
+from wizard.ui import ask_choice, ask_secret, print_header, print_info, print_success
+
+
+@dataclass
+class SearchStepResult:
+    search_provider: SearchProvider | None  # None = skip
+    search_api_key: str | None
+    fetch_provider: WebProvider | None  # None = skip
+    fetch_api_key: str | None
+
+
+def run_search_step(step_label: str = "Step 3/3") -> SearchStepResult:
+    print_header(f"{step_label} · Web Search & Fetch (optional)")
+    provided_keys: dict[str, str] = {}
+
+    search_options = [f"{p.display_name}  —  {p.description}" for p in SEARCH_PROVIDERS]
+    search_options.append("Skip for now  (agent still works without web search)")
+
+    idx = ask_choice("Choose a web search provider", search_options, default=0)
+
+    search_provider: SearchProvider | None = None
+    search_api_key: str | None = None
+    if idx >= len(SEARCH_PROVIDERS):
+        search_provider = None
+    else:
+        search_provider = SEARCH_PROVIDERS[idx]
+        if search_provider.env_var:
+            print()
+            search_api_key = ask_secret(f"{search_provider.env_var}")
+            provided_keys[search_provider.env_var] = search_api_key
+            print_success(f"Key will be saved to .env as {search_provider.env_var}")
+
+    print()
+    fetch_options = [f"{p.display_name}  —  {p.description}" for p in WEB_FETCH_PROVIDERS]
+    fetch_options.append("Skip for now  (agent can still answer without web fetch)")
+
+    idx = ask_choice("Choose a web fetch provider", fetch_options, default=0)
+
+    fetch_provider: WebProvider | None = None
+    fetch_api_key: str | None = None
+    if idx < len(WEB_FETCH_PROVIDERS):
+        fetch_provider = WEB_FETCH_PROVIDERS[idx]
+        if fetch_provider.env_var:
+            if fetch_provider.env_var in provided_keys:
+                fetch_api_key = provided_keys[fetch_provider.env_var]
+                print()
+                print_info(f"Reusing {fetch_provider.env_var} from web search provider")
+            else:
+                print()
+                fetch_api_key = ask_secret(f"{fetch_provider.env_var}")
+                provided_keys[fetch_provider.env_var] = fetch_api_key
+                print_success(f"Key will be saved to .env as {fetch_provider.env_var}")
+
+    return SearchStepResult(
+        search_provider=search_provider,
+        search_api_key=search_api_key,
+        fetch_provider=fetch_provider,
+        fetch_api_key=fetch_api_key,
+    )