Self-install into canonical layout on both platforms, --no-copy to opt out

Windows: --install-service creates %ProgramFiles%\gpu-turnstile and
%ProgramData%\gpu-turnstile, copies the exe and (if absent) the env
file in, and registers the copy. Linux: binary goes to
/var/lib/gpu-turnstile (not /usr/local/sbin: replacing a running binary
needs directory write, which must not be granted on a shared system dir
to a sandboxed service). --no-copy registers the current location
as-is on both platforms.

internal/service/service_other.go

@@ -28,8 +28,8 @@ func Run(run func(ctx context.Context) error) error {
 	return run(ctx)
 }
 
-// Install is unsupported on non-Windows platforms.
-func Install(string) error { return errUnsupported }
+// Install is unsupported on non-Windows, non-Linux platforms.
+func Install(string, bool) error { return errUnsupported }
 
 // Remove is unsupported on non-Windows platforms.
 func Remove() error { return errUnsupported }