openai/gpt-chat-latest → A (5:1)

Side A consolidates duplicated test infrastructure into shared utilities by introducing reusable helpers such as `run-cargo-build-release!`, `slug-server-env`, shared test assertions, configurable OAuth mock behavior, and `complete-registration!`, then updates multiple integration test suites to use them. This reduces maintenance burden and centralizes behavior across the test codebase, whereas Side B only removes a redundant zero-ratio guard in `apply_vote` and adjusts a single test to match the revised semantics.