Makefile: use sol service restart in install-service
sol service start is a no-op when the service is already running, so
make install-service used to ship new code without actually reloading
the Python process — today's gemini-tokens fix needed a separate
sol service restart after the install to go live. sol service restart
is a superset of start on both platforms (systemctl restart activates
inactive units; launchctl kill SIGTERM is best-effort followed by
kickstart), so swapping it in picks up code changes without regressing
the fresh-install path.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>