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/sdlc/assets/architecture.puml

@@ -0,0 +1,38 @@
+@startuml sdlc-architecture
+skinparam componentStyle rectangle
+skinparam defaultFontName Arial
+skinparam backgroundColor #FAFAFA
+
+package "sdlc Skill" {
+  component "SKILL.md\n(instructions)" as SKILL
+  component "assets/\nphase-checklist.md" as CHECKLIST
+  component "evals/evals.json" as EVALS
+}
+
+package "Project Artifacts (specs/)" {
+  component "requirements.md" as R
+  component "design.md" as D
+  component "tasks.md" as T
+  component "impl-plan.md" as I
+  component "STATUS.md\n(resume point)" as STATUS
+  component "crs/CR-N-*.md\n(change requests)" as CR
+}
+
+package "Codebase" {
+  component "source code" as CODE
+  component "tests" as TESTS
+}
+
+actor Developer
+
+Developer --> SKILL : describe project / "continue"
+SKILL --> R : phase 1
+SKILL --> D : phase 2
+SKILL --> T : phase 3
+SKILL --> I : phase 4
+SKILL --> CODE : phase 5
+SKILL --> TESTS : phase 6
+SKILL --> STATUS : tracks progress
+SKILL --> CR : change requests
+CHECKLIST ..> SKILL : phase gate rules
+@enduml