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/docs-rag/assets/workflow.puml

@@ -0,0 +1,24 @@
+@startuml docs-rag-workflow
+skinparam defaultFontName Arial
+skinparam backgroundColor #FAFAFA
+
+actor Developer
+participant "docs-rag\nSkill" as SKILL
+participant "data/index.json" as INDEX
+participant "docs/*.docx" as DOCS
+
+Developer -> SKILL : 3GPP question
+SKILL -> INDEX : read index
+INDEX --> SKILL : entries (keywords, summary, path)
+SKILL -> SKILL : match query vs keywords & summary
+
+alt summary sufficient
+  SKILL --> Developer : answer from summary\n+ cite spec + version
+else need deeper detail
+  SKILL -> DOCS : read source file
+  DOCS --> SKILL : full spec content
+  SKILL --> Developer : detailed answer\n+ cite spec + version
+else no match
+  SKILL --> Developer : "No matching document found"
+end
+@enduml