Nothing builds the projects that cargo oxide new generates #1763

Nothing builds what cargo oxide new generates. The six scaffold_* tests in cargo-oxide/src/commands/tests.rs read the generated files as text: the launch contract, the single git source, rustfmt cleanliness, .gitignore, the repository URL. check-host-api-paths.sh pattern-matches the templates for removed paths. None of them compiles the project, so a change to cuda-host or cuda-core can break the first project a new user creates while every check stays green. The scaffold has needed fixes before: status-guard.yml cites #1193 for its import order.

Both templates build on main (8d82548) today. I generated the sync and the --async project with the tree's cargo-oxide, redirected their git source to the checkout, and ran cargo oxide build on each.

I'll open a PR that adds this as a step in examples-compile, after the example compile, so it reuses that job's backend and target dir.