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

skills/commit-message/assets/workflow.puml

@@ -0,0 +1,22 @@
+@startuml commit-message-workflow
+skinparam defaultFontName Arial
+skinparam backgroundColor #FAFAFA
+
+actor Developer
+participant "commit-message\nSkill" as SKILL
+participant "git" as GIT
+
+Developer -> SKILL : "commit these changes"
+SKILL -> GIT : git status
+GIT --> SKILL : staged files list
+SKILL -> GIT : git diff --cached
+GIT --> SKILL : diff output
+SKILL -> SKILL : draft Conventional Commits message
+SKILL --> Developer : proposed message
+alt confirmed
+  Developer -> GIT : git commit -m "..."
+else refine
+  Developer -> SKILL : feedback
+  SKILL --> Developer : revised message
+end
+@enduml