feat(codegen): add configurable docs generation (README, AGENTS.md, MCP, Skills)

- Add DocsConfig interface: { readme, agents, mcp, skills } with boolean flags
- Defaults: readme + agents on, mcp + skills opt-in. docs: true enables all.
- generateAgentsDocs(): structured AGENTS.md for LLM consumption with TOOL
  sections, INPUT/OUTPUT schemas, WORKFLOWS, and ERROR HANDLING
- generateMcpConfig(): mcp.json with typed inputSchema per command (JSON Schema)
- generateSkills(): per-command .md skill files for agent systems
- Wire into cli/index.ts orchestrator with config-driven conditional generation
- 22 tests, 17 snapshots covering all formats and config combinations

Author: pyramation