`checks.yml` runs `cargo fmt --check`, and it has been failing since the round-1
audit fixes: I gated those on `cargo build` and `cargo clippy` but never ran fmt,
so three files drifted then and eight more this round. Pure formatting — no
behaviour change; clippy stays at zero and all 70 backend tests still pass.
Worth noting for next time: clippy passing is not evidence fmt does.
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
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