feat(convert): generate PLAYBOOKS.md from Claude Code skills

[duyluann]

Problem

Claude Code skills (ops4life-add-app, ops4life-learning-web, ops4life-insights) are slash commands with multi-step checklists. No equivalent exists in Gemini CLI, GitHub Copilot, or OpenAI Codex.

Currently /convert warns users to reference .claude/references/ and .claude/skills/ manually.

Proposed Solution

When /convert runs, generate a PLAYBOOKS.md that flattens each skill's checklist into a plain markdown runbook — usable as a reference in any AI tool without Claude Code.

Acceptance Criteria

• /convert generates PLAYBOOKS.md alongside the target config file
• Each skill becomes a titled section with numbered steps
• Source skill file path annotated per section
• Works for all 3 targets (Gemini CLI, Copilot, Codex)

Ref: #11