principle-migrate-callers-then-delete-legacy-apis

# Migrate Callers Then Delete Legacy APIs When we decide a new API is the right design, migrate callers and remove the old API in the same refactor wave instead of preserving compatibility layers. **Rule:** - Do not keep legacy API paths only because internal callers still exist - Inventory callers, migrate them, and delete the old API immediately - Treat temporary adapters as exceptional and time-boxed, not default architecture - Update tests to assert the new contract, and delete tests that only protect pre-refactor implementation details **When this applies:** - No external users depend on backward compatibility - The project can absorb coordinated breaking changes - The new API is part of a simplification or refactor initiative Keeping both old and new APIs creates dual-path complexity, slows cleanup, and makes the codebase feel append-only.