To elaborate on @Byku answer, a hacker who did break into your device would not benefit from trying to connect to another Wifi, if there is already any kind of network connectivity to your phone. And nothing an attacker would do would cause an internal chrome page to open in Vanadium. So these two things are definitely not at all indicative of a successful hacking attempts. However, as you yourself was thinking, an attacker who lives close to you might attempt to make their router impersonate a Wifi network you have been connected to, so your device would auto-connect to their network, so they can spy on your activity. But since your device did not successfully connect to that Wifi network, that does not appear to be what happened here, or at least wasn't a successful attack.
The microphone indicator sometimes staying lit after you have used the microphone, staying lit until you reboot the device, is as mentioned a known upstream bug. If the microphone indicator lights up unexpectedly, when not having used microphone or been asked for microphone permissions, that on the other hand might be a strong indicator an app did access the microphone.
As far as I know, Session is not recommended for voice and video calls anyway, since they have not secured or implemented any anonymity for that yet. At least that was the situation a year ago. So ideally you would not grant microphone or webcam access to Session at all.