> But we're not an ant colony to them
Tri-Solaris technologically stomps humanity throughout the series. Humanity was ignorant of the dark forest, and Tri-Solaris knew that. Further, they're able to suppress the Sun's broadcast capability. From their vantage point there was no feasible way for humanity to become aware of the dark forest. Their misunderstanding of humans is a central plot point. By every single measure Tri-Solaris had the advantage in a massive way.
> Why? They have their stealth probe
It was not stealthy. Humanity literally saw the probe pull ahead of the fleet and knew the probe was coming 50+ years before it arrived. Sometimes hiding behind an asteroid or planet is not stealth.
> They were destroyed because their coordinates were broadcasted.
No, the Tri-Solaris civilization still existed near the end of the universe. Their planet was destroyed, but they lived on as a space faring species.
> How? They aren't any less stealthy than sattelites, tv, or radio.
Do you recall what light-speed capable ships do to the fabric of the universe?