Mojo nightly drift: tests fail against the latest nightly

[github-actions]

The weekly drift check failed against the latest Mojo nightly.

CI is pinned to 1.0.0b3.dev2026073014 and stays green, so no PR is blocked -- but
the latest nightly (Mojo 1.0.0b3.dev2026080206 (7db826ea)) no longer builds this repo.

Run: https://github.com/conorbronsdon/mojo-template/actions/runs/30830650961

Fix the breakage, then bump MOJO_VERSION in .github/workflows/test.yml
and .github/workflows/docs.yaml to the nightly that passes.

[github-actions]

The weekly drift check failed against the latest Mojo nightly.

CI is pinned to 1.0.0b3.dev2026073014 and stays green, so no PR is blocked -- but
the latest nightly (Mojo 1.1.0.dev2026081005 (8d5ffe71)) no longer builds this repo.

Run: https://github.com/conorbronsdon/mojo-template/actions/runs/31399437288

Fix the breakage, then bump MOJO_VERSION in .github/workflows/test.yml
and .github/workflows/docs.yaml to the nightly that passes.