improve-codebase-architecture

Analyze codebases for architectural friction and propose module-deepening refactors as testability improvements.

• Explores codebases organically to surface shallow modules, tightly-coupled components, and untested seams rather than following rigid heuristics
• Applies John Ousterhout's "deep module" principle: small interfaces hiding large implementations for better testability and AI navigability
• Generates multiple radically different interface designs (minimalist, flexible, caller-optimized, ports & adapters) via parallel sub-agents, then recommends the strongest approach
• Creates GitHub issue RFCs documenting the problem space, design trade-offs, and refactoring rationale