refactor: flatten Microsoft skills from nested to flat directory structure

Rewrote sync_microsoft_skills.py (v4) to use each SKILL.md's frontmatter
'name' field as the flat directory name under skills/, replacing the nested
skills/official/microsoft/<lang>/<category>/<service>/ hierarchy.

This fixes CI failures caused by the indexing, validation, and catalog
scripts expecting skills/<id>/SKILL.md (depth 1).

Changes:
- Rewrite scripts/sync_microsoft_skills.py for flat output with collision detection
- Update scripts/tests/inspect_microsoft_repo.py for flat name mapping
- Update scripts/tests/test_comprehensive_coverage.py for name uniqueness checks
- Delete skills/official/ nested directory
- Add 129 Microsoft skills as flat directories (e.g. skills/azure-mgmt-botservice-dotnet/)
- Move attribution files to docs/ (LICENSE-MICROSOFT, microsoft-skills-attribution.json)
- Rebuild skills_index.json, CATALOG.md, README.md (845 total skills)

skills/wiki-onboarding/SKILL.md

@@ -0,0 +1,77 @@
+---
+name: wiki-onboarding
+description: Generates two complementary onboarding guides — a Principal-Level architectural deep-dive and a Zero-to-Hero contributor walkthrough. Use when the user wants onboarding documentation for a codebase.
+---
+
+# Wiki Onboarding Guide Generator
+
+Generate two complementary onboarding documents that together give any engineer — from newcomer to principal — a complete understanding of a codebase.
+
+## When to Activate
+
+- User asks for onboarding docs or getting-started guides
+- User runs `/deep-wiki:onboard` command
+- User wants to help new team members understand a codebase
+
+## Language Detection
+
+Scan the repository for build files to determine the primary language for code examples:
+- `package.json` / `tsconfig.json` → TypeScript/JavaScript
+- `*.csproj` / `*.sln` → C# / .NET
+- `Cargo.toml` → Rust
+- `pyproject.toml` / `setup.py` / `requirements.txt` → Python
+- `go.mod` → Go
+- `pom.xml` / `build.gradle` → Java
+
+## Guide 1: Principal-Level Onboarding
+
+**Audience**: Senior/staff+ engineers who need the "why" behind decisions.
+
+### Required Sections
+
+1. **System Philosophy & Design Principles** — What invariants does the system maintain? What were the key design choices and why?
+2. **Architecture Overview** — Component map with Mermaid diagram. What owns what, communication patterns.
+3. **Key Abstractions & Interfaces** — The load-bearing abstractions everything depends on
+4. **Decision Log** — Major architectural decisions with context, alternatives considered, trade-offs
+5. **Dependency Rationale** — Why each major dependency was chosen, what it replaced
+6. **Data Flow & State** — How data moves through the system (traced from actual code, not guessed)
+7. **Failure Modes & Error Handling** — What breaks, how errors propagate, recovery patterns
+8. **Performance Characteristics** — Bottlenecks, scaling limits, hot paths
+9. **Security Model** — Auth, authorization, trust boundaries, data sensitivity
+10. **Testing Strategy** — What's tested, what isn't, testing philosophy
+11. **Operational Concerns** — Deployment, monitoring, feature flags, configuration
+12. **Known Technical Debt** — Honest assessment of shortcuts and their risks
+
+### Rules
+- Every claim backed by `(file_path:line_number)` citation
+- Minimum 3 Mermaid diagrams (architecture, data flow, dependency graph)
+- All Mermaid diagrams use dark-mode colors (see wiki-vitepress skill)
+- Focus on WHY decisions were made, not just WHAT exists
+
+## Guide 2: Zero-to-Hero Contributor Guide
+
+**Audience**: New contributors who need step-by-step practical guidance.
+
+### Required Sections
+
+1. **What This Project Does** — 2-3 sentence elevator pitch
+2. **Prerequisites** — Tools, versions, accounts needed
+3. **Environment Setup** — Step-by-step with exact commands, expected output at each step
+4. **Project Structure** — Annotated directory tree (what lives where and why)
+5. **Your First Task** — End-to-end walkthrough of adding a simple feature
+6. **Development Workflow** — Branch strategy, commit conventions, PR process
+7. **Running Tests** — How to run tests, what to test, how to add a test
+8. **Debugging Guide** — Common issues and how to diagnose them
+9. **Key Concepts** — Domain-specific terminology explained with code examples
+10. **Code Patterns** — "If you want to add X, follow this pattern" templates
+11. **Common Pitfalls** — Mistakes every new contributor makes and how to avoid them
+12. **Where to Get Help** — Communication channels, documentation, key contacts
+13. **Glossary** — Terms used in the codebase that aren't obvious
+14. **Quick Reference Card** — Cheat sheet of most-used commands and patterns
+
+### Rules
+- All code examples in the detected primary language
+- Every command must be copy-pasteable
+- Include expected output for verification steps
+- Use Mermaid for workflow diagrams (dark-mode colors)
+- Ground all claims in actual code — cite `(file_path:line_number)`