Resolve the macOS race budget conflict in favour of the focused scope.
c1f96241 on main extended the whole-package macOS race step from 10m to
12m and pinned that budget in the workflow contract. This branch removes
the whole-package run instead: ./internal/app is already covered by the
Ubuntu "race: app" shard, and macOS only needs the natively-gated tests.
With the focused scope the job drops from 10m47s to ~3m, so the 12m
budget is no longer needed and the two step timeouts (6m + 5m) fit inside
the 15m job budget with headroom.
The contract assertion c1f96241 added is superseded rather than dropped:
pinning both focused commands locks the per-step timeouts, and the
existing checks still block a whole-package regression and require
./internal/app to appear exactly once.
chichuan
20d27f6db9