Add comprehensive swift-docc documentation and architecture guide

[Kyle-Ye]

Summary

This PR adds comprehensive swift-docc documentation to OpenAttributeGraph, including a detailed architecture guide and complete API documentation following OpenSwiftUI conventions.

Changes Made

📚 README Architecture Section

• Added comprehensive architecture explanation covering Attribute, Graph, and Runtime components
• Detailed descriptions of each component's purpose and functionality
• Reference to wickwirew/Runtime for Swift runtime techniques

📖 Swift-DocC Documentation Catalog

• Main Module Documentation: OpenAttributeGraph.md with organized topic structure
• Architecture Guide: Architecture.md with in-depth system design explanation
• Core Components: CoreComponents.md covering fundamental APIs
• Advanced Topics: AdvancedTopics.md for specialized functionality

🔧 API Documentation

Added comprehensive swift-docc documentation for key public APIs:

• Attribute<Value> struct with property wrapper usage examples
• Rule protocol for computed attributes with dependency tracking
• Metadata extensions for runtime type introspection
• Complete code examples using indented format (matching OpenSwiftUI style)

📝 Documentation Structure

OpenAttributeGraph.docc/
├── OpenAttributeGraph.md (main module doc)
├── Architecture.md (system architecture)  
├── CoreComponents.md (fundamental APIs)
└── AdvancedTopics.md (advanced features)

🎨 Formatting & Standards

• All code examples use indented format (4 spaces) instead of markdown fences
• Follows OpenSwiftUI documentation patterns and conventions
• Clean topic organization without nested subheadings
• Proper swift-docc link references and symbol documentation

Architecture Coverage

The documentation thoroughly covers OpenAttributeGraph's architecture:

Attribute System: Reactive property wrappers with automatic dependency tracking, type erasure, rule-based transformations, and efficient value computation.

Graph Management: Dependency network coordination, update orchestration, invalidation tracking, batch processing, and scoped computation contexts.

Runtime Support: Swift runtime type introspection, memory layout manipulation, efficient value comparison, and pointer arithmetic for nested access.

Code Examples

All documentation includes practical code examples:

• Property wrapper usage patterns
• Rule-based computed attributes
• Runtime type introspection
• Dynamic member lookup
• Integration with larger systems

Benefits

• Better Developer Experience: Clear, comprehensive documentation for all public APIs
• Architectural Understanding: In-depth guide to system design and component interaction
• Consistency: Follows established OpenSwiftUI documentation patterns
• Discoverability: Well-organized topic structure for easy navigation
• Swift-DocC Integration: Full compatibility with Xcode documentation browser

Testing

• ✅ Swift-DocC warnings resolved
• ✅ All article references working correctly
• ✅ Code examples properly formatted
• ✅ Documentation builds successfully
• ✅ Follows OpenSwiftUI conventions

Ready for review and integration into the main branch.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 4.81%. Comparing base (75309ed) to head (814c79a).
⚠️ Report is 2 commits behind head on main.

Additional details and impacted files

@@          Coverage Diff          @@
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  Coverage   4.81%   4.81%           
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  Files         28      28           
  Lines        831     831           
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  Hits          40      40           
  Misses       791     791           

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