Add comprehensive development guidelines enforcing least-complex solutions
for bugs and features. Establishes Rule of Three for abstractions,
prohibits drive-by refactors, and requires evidence-based future-proofing.
- Enforces minimal viable diffs that fully resolve issues
- Prevents speculative abstractions without concrete usage
- Requires ADR discussion and evidence for added complexity
- Includes PR checklist and assistant output contract
- Promotes dependency frugality and targeted testing