Add comprehensive Behavior Tree curriculum (10 sessions, 20 hours)

[raisewise0211]

Summary

This PR adds a complete Behavior Tree (BT) educational curriculum consisting of 10 sessions covering fundamental concepts through advanced ROS2 integration. The curriculum is designed to teach the core 30% of BT knowledge that produces 90% of practical results, with emphasis on hands-on understanding through "cause-and-effect" analysis.

Key Changes

• Added 10 comprehensive session documents covering the complete BT learning path:

  • Session 1: FSM limitations and why BT solves them (Tick concept)
  • Session 2: 4 core node types (Control, Decorator, Action, Condition) and state propagation
  • Session 3: Blackboard and Ports for inter-node data sharing
  • Session 4: XML structure definition and toolchain (Factory, Groot2)
  • Session 5: Decorator nodes (Retry, Timeout, Inverter, etc.) with time calculation formulas
  • Session 6: Reactive execution model (ReactiveSequence, ReactiveFallback, Parallel)
  • Session 7: Subtree modularization and hierarchical design patterns
  • Session 8: Custom node development (SyncActionNode vs StatefulActionNode)
  • Session 9: ROS2 Nav2 integration with real-world patterns and anti-patterns
  • Session 10: Comprehensive capstone project (robot patrol scenario)

• Added index page (behavior-tree/index.md) with curriculum overview, learning objectives, and session roadmap

• Updated navigation in mkdocs.yml to include all 10 BT sessions in the main navigation structure

Notable Implementation Details

• Pedagogical approach: Each session follows a consistent structure:

  • "원인과 결과" (cause-and-effect) analysis explaining why each concept exists
  • Visual diagrams and ASCII art for complex concepts
  • Mathematical formulas in dedicated boxes (e.g., retry timeout calculations)
  • 15-minute review sections with fill-in-the-blank exercises and quizzes
  • Forward references to next session

• Practical focus: Curriculum emphasizes real-world usage patterns from BehaviorTree.CPP v4 and ROS2 Nav2, avoiding esoteric features

• Comprehensive capstone: Session 10 integrates all previous concepts through a robot patrol scenario requiring priority trees, decorators, reactive execution, and custom nodes

• Self-contained: Each session can be understood independently while building toward integrated knowledge by session 10

https://claude.ai/code/session_01GUVuwQn1bEdS8Mpyi4rdPP

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