Upgrade Engine

Core principle: Every claimed Rails/Ruby version must be in the CI matrix. Prefer explicit support targets over accidental compatibility.

HARD-GATE

Before claiming support for a Rails/Ruby version:
  1. bundle exec rake zeitwerk:check        # verify autoloading on each version
  2. bundle exec rspec                       # full suite per matrix version
  3. CI matrix must pass — not just main Rails version

DO NOT ship compatibility changes without verifying both autoloading and full suite.

Core Process