The macOS self-update relaunches and installs over the app it derives via
resolve_hermes_desktop_app (.../Hermes.app/Contents/MacOS/Hermes ->
.../Hermes.app). That derivation is load-bearing for both the ditto
install target and the auto-relaunch (open <app>), but had no test.
Add unit coverage:
- resolve_hermes_desktop_app_finds_built_bundle: a fake built release tree
resolves to the .app bundle on macOS (and the exe elsewhere).
- resolve_hermes_desktop_app_is_none_without_a_build: no build => None.
Verified the positive test FAILS if the .app parent-walk is wrong (e.g.
one too few .parent() hops), so it's a real guard against a regression
that would break the post-update relaunch target.
cargo test -> 17 passed.
39fee4f3bc