feat(readme): optimize README for open source promotion with semantic layer vision

[mars167]

📝 Description

This PR optimizes both Chinese and English README files to better promote the project in the open source community, while clearly communicating our vision of building a semantic layer for codebases.

🎯 Key Improvements

1. Compelling Headlines

• Chinese: "为代码库添加语义层，让 AI 从'读代码'进化到'懂代码'"
• English: "Adding a Semantic Layer to Your Codebase, Enabling AI to Evolve from 'Reading Code' to 'Understanding Code'"

2. Clear Value Proposition

• Subtitle: "Code semantics should be versioned and traceable, just like code itself"
• Emphasizes our core vision: semantic layer + versioning + traceability

3. Enhanced Why git-ai Section

• Added Performance Metrics: "10k files indexed in < 30s, search response < 100ms"
• Added Community Badges: npm downloads badge for social proof
• Maintained focus on Hyper RAG, Versioned Semantics, and Full Lifecycle Support

4. Improved Architecture Diagram

• Updated "DSR Generator" → "DSR (Deterministic Semantic Record)" to emphasize DSR as the core component
• Enhanced visual clarity of the semantic timeline concept

5. Real Output Examples

• Added actual output examples in Quick Start section to demonstrate immediate value
• Shows concrete JSON output that users can expect

6. Technical Details Migration

• Moved detailed technical documentation to docs/zh-CN/technical-details.md
• Kept README focused on marketing and quick adoption

🚀 Impact

• Better Open Source Appeal: Clear value proposition that resonates with developers
• Reduced Learning Curve: Immediate examples show real-world benefits
• Vision Alignment: Communicates our long-term goal of AI-native development workflows without sounding overly commercial
• Performance Transparency: Concrete metrics build trust and credibility

✅ Testing

All tests pass ✅

• 9/9 tests successful
• Both README files render correctly with Mermaid diagrams
• All documentation links are valid

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Let AI evolve from "reading code" to "understanding code" ⭐