Match the legacy entry against this checkout's desktop-run.sh instead of any
desktop-run.sh, and delete the legacy icon files only after that entry or the
old artwork proves ownership. Quote and escape Exec arguments as the Desktop
Entry specification requires, so a checkout path with reserved characters no
longer produces an invalid entry, and escape the Path value.
Use StartupWMClass=RiotClientServices in both entries: Darling derives WM_CLASS
from -[NSProcessInfo processName], the basename of argv[0], and the launcher
starts .../RiotClientServices. "Riot Client" is only the bundle display name,
so the checkout entry never matched the window. Both entries now share
Name/GenericName/Comment/Icon/Keywords/Categories and a test keeps them in
sync; Terminal stays different because the checkout entry logs to
build/desktop-launch.log while the packaged entry runs the session in a
terminal.
Also drop the stray top-level icon copies, handle dangling legacy symlinks,
name the icon for assistive technology, document the alias and menu entry, and
cover the helper with disposable-HOME tests.
