setup: reinstall the git hook from the merged hook-path setting

updateGlobalSettings reinstalled the git hook (on --force or --absolute-git-hook-path) with the target file's absolute_git_hook_path alone. With the setting only in settings.local.json and the write going to settings.json, --force --telemetry=false replaced a working absolute-path hook with a PATH-dependent one. Use the merged view after the save, as setupAgentHooksNonInteractive does.