Add educational resources for Claude Code's parallel execution mechanism

[Copilot]

Addresses request to learn Claude Code's core interactive mechanism - "不等他结束，完全在过程中互动" (non-blocking parallel execution).

Changes

Learning Resources (Chinese)

• docs/claude-code-交互机制学习指南.md - Technical deep-dive on v7's background execution and notification bus architecture
• docs/claude-code-交互机制可视化.md - ASCII diagrams comparing serial (v0-v6) vs parallel (v7+) execution patterns
• docs/学习成果总结.md - Learning path and summary

Interactive Demo

• demo_interactive_mechanism.py - Standalone script demonstrating serial vs parallel execution
  • No API key required
  • Shows 50% performance improvement in parallel mode
  • Includes timeout handling and proper task ID collision avoidance (8-char UUIDs)

Documentation Updates

• Updated README_zh.md with quick start section and navigation to new resources

Key Technical Concepts

v7 Background Execution:

# Serial (v0-v6): blocks main agent
result = Task(prompt="analyze code")  # waits...

# Parallel (v7+): returns immediately
task_id = Task(prompt="analyze code", run_in_background=True)
# main agent continues working, gets notification when complete

Architecture:

• BackgroundManager: Thread-based parallel task execution with task ID prefixes (a=agent, b=bash, t=teammate)
• Notification bus: Push-based (not polling) attachment injection into message stream
• Thread-safe queue for cross-thread completion signals

Performance: O(max(tasks)) vs O(sum(tasks)) in serial mode

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