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/skills/public/chart-visualization/references/generate_path_map.md

@@ -0,0 +1,20 @@
+# generate_path_map — 路径地图（中国）
+
+## 功能概述
+基于高德地图展示中国境内的路线或行程，按顺序连接一系列 POI，适用于物流路线、旅游规划、配送轨迹等。
+
+## 输入字段
+### 必填
+- `title`: string，必填且≤16 字，描述路线主题。
+- `data`: array<object>，至少 1 个路线对象。
+- `data[].data`: string[]，必填，包含该路线上按顺序排列的中国境内 POI 名称。
+
+### 可选
+- `width`: number，默认 `1600`。
+- `height`: number，默认 `1000`。
+
+## 使用建议
+POI 名称必须具体且位于中国（如“西安市钟楼”“杭州西湖苏堤春晓”）；若需多条线路，可在 `data` 中添加多段对象。
+
+## 返回结果
+- 返回路径地图 URL，并在 `_meta.spec` 中保留标题与 POI 列表；若配置 `SERVICE_ID`，还会记录到“我的地图”。