feat(architecture): introduce Frank v6 modular skills-centric system

Phase 1-4 Complete: Setup, Core Extraction, ITIL Specialty, Documentation

- Created v6/ folder with 3-layer architecture (core + skills + specialties)
- Extracted Frank.core.agent.md with universal personas and base commands
- Copied 7 skill modules (CRAFT, CoT, ToT, RAG, Markdown, Mermaid, Advanced Reasoning)
- Created specialty.itil.instructions.md for IT Service Management (ITIL v4)
- Added comprehensive ARCHITECTURE.md with usage patterns and migration guide
- Created v6/copilot-instructions.md for VS Code integration
- Organized legacy DOCX files into _Frank_/docx/ subdirectory
- Updated all cross-references to use v6 relative paths

Design Principles:
- Portability first: zero environment-specific paths
- Modular composition: load only what you need
- Multi-specialty support: combine domain experts
- Version compatibility: all files tagged v6.0

Ref: Session plan in /memories/session/plan.md
Next: Phase 3 (remaining specialties: devops, prompt-engineering, data-analysis, sccm)

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