Add comprehensive project architecture documentation

[Copilot]

Overview

This PR addresses the issue "总结一下项目架构" (Summarize the project architecture) by adding detailed bilingual documentation explaining the zdocs project's architecture, components, and design decisions.

What's Added

ARCHITECTURE.md

A comprehensive architecture document covering:

• Project Overview: Explains zdocs as a documentation tool for Zig modules, similar to Zig's standard library documentation but supporting all Zig modules
• Three-Tier Architecture Design:
  • CLI/HTTP Server Layer (src/main.zig): Command-line interface, HTTP server, static file serving, and source code archival
  • WebAssembly Processing Layer (src/wasm/): AST parsing (Walk.zig), declaration management (Decl.zig), HTML rendering (html_render.zig), and Markdown processing (markdown.zig)
  • Web Frontend Layer (www/): TypeScript/Bun-based web server, WASM interface, and browser-side documentation UI
• Data Flow Diagram: Visual representation showing how user requests flow through the system
• Build System: Documentation of build targets, WASM compilation, and the dual-mode approach (embedded vs. standalone)
• Deployment Modes: Embedded mode (single binary), development mode (hot reload), and standalone web server
• Key Features: Module support, source code browsing, search functionality, and documentation comment parsing
• Complete Directory Structure: Detailed breakdown of the project organization
• Dependencies: Zig 0.14.x, Bun 1.2.18+, TypeScript
• Extension Points: Guidelines for adding new documentation formats, Zig language features, and UI customizations
• Performance Considerations: WASM performance, incremental parsing, caching, and multi-threading
• Development Workflow: Commands and best practices for contributing

README.md Updates

Added a new "documentation" section that links to the architecture documentation, making it easily discoverable for new contributors and users who want to understand the project structure.

Benefits

• Bilingual Support: Documentation in both Chinese and English serves the international developer community
• Comprehensive Coverage: 13 major sections covering all architectural aspects
• Practical Information: Includes actual build commands, development workflows, and code examples
• Clear Component Separation: Explains how the three layers interact and their individual responsibilities
• Onboarding: Significantly reduces the learning curve for new contributors

Documentation Highlights

The architecture follows a clean separation of concerns:

1. The CLI/Server handles user interaction and serves static assets
2. The WASM layer performs heavy lifting: parsing Zig source code, analyzing ASTs, and generating documentation HTML
3. The Web frontend provides both a development server (with multiple package support) and an embedded browser UI

This design enables zdocs to be distributed as a single binary while also supporting a more flexible web-based deployment for serving documentation of multiple Zig packages simultaneously.

Original prompt

总结一下项目架构

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