feat: Add 19 Claude Code skills for document workflow

Skills included:
- Review (6): rr, rp, rf, rd, ru, rt
- Write (5): wp, wf, wd, wu, wt
- Modify (6): mr, mp, mf, md, mu, mt
- Utils (2): iter, up

Supports complete document lifecycle:
RequirementsDoc → PRD → FeatureSummary → DevelopmentPlan → UIDesign → tasks

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

.gitignore

@@ -0,0 +1,15 @@
+# 文档目录（各项目自己生成）
+doc/
+
+# 其他开发文件
+write-skills/
+.codex/
+
+# macOS
+.DS_Store
+
+# IDE
+.idea/
+.vscode/
+*.swp
+*.swo