chore: restructure skills repo with new agents and skill bundles

- Add new skills: deep-dive, docs-rag, meta-creator, ppt-maker, sdlc
- Add agent configs: g-assistent, meta-creator, sdlc with prompt files
- Add reference docs for custom agents and skills specification
- Add utility scripts: install-agents.sh, orchestrate.py, puml2svg.sh
- Update README and commit-message skill config
- Remove deprecated skills: codereview, python, testing, typescript
- Add .gitignore

.kiro/agents/g-assistent.json

@@ -0,0 +1,10 @@
+{
+  "name": "g-assistent",
+  "description": "通用开发助手，自动路由到合适的 skill 处理用户请求。支持代码分析、代码审查、提交信息、系统设计、测试、文档查询等开发任务。",
+  "prompt": "file://prompts/g-assistent.md",
+  "tools": ["fs_read", "fs_write", "execute_bash", "grep", "glob", "code", "fetch"],
+  "allowedTools": ["fs_read", "grep", "glob", "code", "fetch"],
+  "resources": [
+    "skill://.kiro/skills/**/SKILL.md"
+  ]
+}