The native smoke only ran inside desktop-bundled-release, and it checked out
its test scripts at the same commit as the artifact it fetched. Changing a
test therefore meant a new commit, and a new commit meant a full signed
build (about an hour per platform) just to rerun the smoke.
Add workflow_dispatch: `sha` picks the staged artifact to fetch, and the
scripts come from the ref the dispatch runs on. Release callers are
unchanged.
1744a19e0d