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/deep-dive/assets/architecture.puml

@@ -0,0 +1,27 @@
+@startuml deep-dive-architecture
+skinparam componentStyle rectangle
+skinparam defaultFontName Arial
+skinparam backgroundColor #FAFAFA
+
+package "deep-dive Skill" {
+  component "SKILL.md\n(instructions + triggers)" as SKILL
+  component "assets/\nreport-template.md\n(11 section skeletons)" as TMPL
+  component "evals/evals.json" as EVALS
+}
+
+package "Input Sources" {
+  component "File path(s)\n(src/, docs/, manifests)" as FILES
+  component "URL\n(fetched content)" as URL
+  component "Pasted text /\nTopic name" as TEXT
+}
+
+package "Output" {
+  component "deep-dive-{subject}.md\n(structured report)" as REPORT
+}
+
+SKILL --> TMPL : loads 11-section template
+SKILL --> FILES : reads source files
+SKILL --> URL : fetches content
+SKILL --> TEXT : analyzes inline
+SKILL --> REPORT : writes report
+@enduml