feat: add douban-skill + enhance skill-creator with development methodology

New skill: douban-skill
- Full export of Douban (豆瓣) book/movie/music/game collections via Frodo API
- RSS incremental sync for daily updates
- Python stdlib only, zero dependencies, cross-platform (macOS/Windows/Linux)
- Documented 7 failed approaches (PoW anti-scraping) and why Frodo API is the only working solution
- Pre-flight user validation, KeyboardInterrupt handling, pagination bug fix

skill-creator enhancements:
- Add development methodology reference (8-phase process with prior art research,
  counter review, and real failure case studies)
- Sync upstream changes: improve_description.py now uses `claude -p` instead of
  Anthropic SDK (no ANTHROPIC_API_KEY needed), remove stale "extended thinking" ref
- Add "Updating an existing skill" guidance to Claude.ai and Cowork sections
- Restore test case heuristic guidance for objective vs subjective skills

README updates:
- Document fork advantages vs upstream with quality comparison table (65 vs 42)
- Bilingual (EN + ZH-CN) with consistent content

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

README.md

@@ -38,13 +38,35 @@ Professional Claude Code skills marketplace featuring 43 production-ready skills
 
 The `skill-creator` is the **meta-skill** that enables you to build, validate, and package your own Claude Code skills. It's the most important tool in this marketplace because it empowers you to extend Claude Code with your own specialized workflows.
 
-### Why skill-creator First?
+### Why This skill-creator?
 
-- **🎯 Foundation**: Learn how skills work by creating your own
-- **🛠️ Complete Toolkit**: Initialization, validation, and packaging scripts included
-- **📖 Best Practices**: Learn from production-ready examples
-- **🚀 Quick Start**: Generate skill templates in seconds
-- **✅ Quality Assurance**: Built-in validation ensures your skills meet standards
+This is a **production-hardened fork** of [Anthropic's official skill-creator](https://github.com/anthropics/skills/tree/main/skills/skill-creator), born from building real skills and hitting every wall the official version doesn't warn you about.
+
+**The official skill-creator tells you _what_ to build. Ours also tells you _what not to try_ — and why.**
+
+| You're trying to... | Official | This Fork |
+|---------------------|----------|-----------|
+| Research before building | "Check available MCPs" (5 lines) | 8-channel search protocol with decision matrix: Adopt / Extend / Build |
+| Create a skill interactively | Prose-based instructions | 9 structured AskUserQuestion checkpoints — user never loses context |
+| Avoid common mistakes | No guidance | Cache edit warnings, prerequisite checks, security scan gate |
+| Know the architecture options | Not mentioned | Inline vs Fork decision guide with examples (choosing wrong silently breaks your skill) |
+| Validate before shipping | Basic YAML check | Expanded validator (all frontmatter fields, path reference integrity, whitespace issues) |
+| Catch security issues | No tooling | `security_scan.py` with gitleaks integration — hard gate before packaging |
+| Learn from real failures | No failure cases | Battle-tested methodology with documented failure patterns and gotchas |
+
+**Quality comparison** (independent audit, 8 dimensions):
+
+| Dimension | Official | This Fork |
+|-----------|----------|-----------|
+| Actionability | 7 | 9 |
+| Error Prevention | 5 | 9 |
+| Prior Art Research | 4 | 9 |
+| Counter Review Process | 4 | 8 |
+| Real-World Lessons | 3 | 8 |
+| User Experience | 4 | 9 |
+| **Total (out of 80)** | **42** | **65** |
+
+> Full methodology: [skill-creator/references/skill-development-methodology.md](./skill-creator/references/skill-development-methodology.md)
 
 ### Quick Install