Design Principles Audit

Audit the codebase against well-known design principles. Produce a scored DESIGN_AUDIT.md with prioritized remediation actions.

Core principle: Investigate, do not pattern-match. Read the actual code to determine whether a violation is genuine, intentional, or a false positive. Only flag findings with specific file:line evidence.

Prerequisite check

git --version 2>/dev/null && git rev-parse --is-inside-work-tree 2>/dev/null

If not in a git repository, warn but proceed — git history will be unavailable but file analysis still works.