Tutorial Manager (framework)

[JohnLudlow]

Summary:
Event-driven tutorial manager framework: state machine for progression, trigger registration, persistence, and content loader (markdown-first).

Description:
Implement a robust Tutorial Manager that:

• Listens for game events and evaluates trigger conditions
• Manages tutorial progression state (in-progress, paused, completed)
• Persists progress across sessions and supports resumable tutorials
• Loads tutorial content authored as markdown-first files with front-matter
• Exposes an API for UI components to advance/skip/reset tutorials
• Integrates with analytics to emit tutorial start/complete/drop-off events

Acceptance criteria:

• API for registering triggers and starting/stopping tutorials
• State machine with unit tests for transitions and edge cases
• Save/load of tutorial progress with integration test
• Content loader that parses front-matter .tutorial.md files and validates required fields
• Sample tutorial content in docs/plans/4x-game/systems/onboarding/tutorial-manager.md
• Documentation for content authors and loader usage

Parent: #1
Docs: docs/plans/4x-game/systems/onboarding/tutorial-manager.md