feat: add security guides and sanitize external links across repo

New articles:
- the-security-guide.md: "The Shorthand Guide to Securing Your Agent" (595 lines)
  Attack vectors, sandboxing, sanitization, OWASP Top 10, observability
- the-openclaw-guide.md: "The Hidden Danger of OpenClaw" (470 lines)
  Security analysis of OpenClaw, MiniClaw thesis, industry evidence

External link sanitization (22 files across EN, zh-CN, zh-TW, ja-JP, .cursor):
- Removed third-party GitHub links from skills and guides
- Replaced with inline descriptions to prevent transitive prompt injection
- Kept official org links (Anthropic, Google, Supabase, Mixedbread)

the-longform-guide.md

@@ -292,7 +292,7 @@ Phase 5: VERIFY (use build-error-resolver if needed) → done or loop back
 
 You can set it using `/statusline` - then Claude will say you don't have one but can set it up for you and ask what you want in it.
 
-See also: https://github.com/sirmalloc/ccstatusline
+See also: ccstatusline (community project for custom Claude Code status lines)
 
 ### Voice Transcription
 
@@ -323,16 +323,16 @@ alias q='cd ~/Desktop/projects'
 
 **Agent Orchestration:**
 
-- https://github.com/ruvnet/claude-flow - Enterprise orchestration platform with 54+ specialized agents
+- claude-flow — Community-built enterprise orchestration platform with 54+ specialized agents
 
 **Self-Improving Memory:**
 
-- https://github.com/affaan-m/everything-claude-code/tree/main/skills/continuous-learning
+- See `skills/continuous-learning/` in this repo
 - rlancemartin.github.io/2025/12/01/claude_diary/ - Session reflection pattern
 
 **System Prompts Reference:**
 
-- https://github.com/x1xhlol/system-prompts-and-models-of-ai-tools - Collection of system prompts (110k stars)
+- system-prompts-and-models-of-ai-tools — Community collection of AI system prompts (110k+ stars)
 
 **Official:**