relay-eval: fill in indigo for remaining hosts + add t4tlabs entry
the rest of the tracked relays all run indigo. this completes the
impl column so every row links to its source repo instead of
rendering em-dash.
also adds a proper ops entry for relay.t4tlabs.net (was falling
through to the auto-derived default).
Co-Authored-By: Claude Opus 4 (1M context) <noreply@anthropic.com>