Phase 4 Architecture Plan Complete

Status: Ready for review
Timeline: 3-4 weeks (MVP in 2 weeks, advanced features in 4 weeks)
Core Components: PatternMatchProcessor + PatternMatchPlugin (exhaustiveness checking), NoneContextPlugin (context-aware type inference), AST parent tracking, enhanced error messages with suggestions
Key Decisions: Rust-like match syntax, tag-based dispatch for sum types, expression-based matching with type checking, go/types integration for accurate inference, detailed error diagnostics with code suggestions
Complexity: Medium-High (new subsystems but builds on Phase 3 foundation)

Details: /Users/jack/mag/dingo/ai-docs/sessions/20251118-150059/01-planning/initial-plan.md
Open Questions: /Users/jack/mag/dingo/ai-docs/sessions/20251118-150059/01-planning/gaps.json (10 architectural decisions need user input)
