docs: Add ARCHITECTURE.md and improve README.md with better content separation

[Copilot]

This PR adds a comprehensive ARCHITECTURE.md file following the architecture.md standard format and improves the README.md to better serve different audiences through clear content separation.

What's Added

New ARCHITECTURE.md

A comprehensive technical architecture document that includes:

• System Overview: High-level architecture with 3-layer design (Applications, Core Libraries, Foundation)
• Architecture Principles: Zero-copy design, arena allocation, visitor patterns, and shared infrastructure
• Core Components: Detailed documentation of 15+ crates with dependencies and purposes
• Technical Implementation: Detailed performance explanations moved from README.md
• AST Design Principles: Explanation of Oxc AST vs estree differences and design rationale
• Quality Attributes: Performance targets, correctness strategies, and maintainability approaches
• Design Decisions: Key architectural choices with rationale and trade-offs
• Development Infrastructure: Testing strategies, tooling, and development practices

Improved README.md

The README.md has been streamlined to be more user-focused:

• Clearer Introduction: Emphasizes user benefits (performance, reliability, modularity, developer experience)
• Simplified Technical Sections: Removed detailed implementation explanations while keeping performance benchmarks
• Better Getting Started: Maintained practical usage examples and installation guides
• Cross-Referenced Architecture: Added link to ARCHITECTURE.md for technical details

Content Separation Strategy

The documentation now follows a clear separation of concerns:

• README.md: User-focused introduction, getting started guides, and high-level benefits for users wanting to adopt Oxc tools
• ARCHITECTURE.md: Technical implementation details, design decisions, and development practices for contributors and maintainers

This approach ensures that users can quickly understand what Oxc offers and how to get started, while developers and contributors have access to comprehensive technical documentation about the system's architecture and design principles.

The ARCHITECTURE.md accurately reflects Oxc's current capabilities and avoids mentioning unimplemented features like incremental processing, type inference, and error recovery.

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[Boshen]

@copilot improve README.md and move technical contents to ARCHITECTURE.MD

[Copilot]

@copilot improve README.md and move technical contents to ARCHITECTURE.MD

I've improved README.md and moved technical content to ARCHITECTURE.md as requested. The README.md is now more user-focused while ARCHITECTURE.md contains the detailed implementation explanations. Changes include:

• Simplified README.md introduction to focus on user benefits
• Moved "How is it so fast?" technical details to ARCHITECTURE.md
• Moved AST design principles and estree differences to ARCHITECTURE.md
• Enhanced ARCHITECTURE.md with development infrastructure details
• Added cross-reference from README.md to ARCHITECTURE.md

Commit: d5d1429

[Boshen]

@copilot we do not have:

• incremental processing
• Type inference
• Error recovery

please remove these mentions from ARCHITECTURE.md

[Copilot]

@copilot we do not have:

• incremental processing
  ...

I've removed all mentions of incremental processing, type inference, and error recovery from ARCHITECTURE.md since these features are not currently implemented in Oxc. The changes include:

• Removed the entire "Incremental Processing" section from architecture principles
• Removed "Type inference (basic)" from oxc_semantic features
• Removed "Error recovery for incomplete code" from oxc_parser features
• Removed "Better error recovery control" from parser design rationale
• Updated scalability section to use "Processing optimization improvements" instead

Commit: 83f624d