Silverado Power Source for Valentine One

I have a 2005 Silverado 2500 LT.  I want to install a permanent connection for a Valentine One radar detector.  Rather than run wiring down beneath the dash, I'd like to tap a power source near the roof.  I think I've found two possibilities.

First, I opened the cover on the dome lights and saw an orange wire.  Based on color, I gather this is an accessory wire.  It seems like this might be okay since the dome lights go out after a few minutes but I'm not sure whether the orange wire powers the map lights or if it stays hot even after the map lights go out because it's connected to something else also.

Second, it seems like there must be an ignition wire that powers the compass and thermometer in the mirror.  Those are off when the car is off and on when on.  The wires that run to the mirror look like they're accessible but the OnStar wiring and mirror dimmer adjustment wiring is in there too (I guess) so I'm not sure what's what.  I think there might be something there I could use if I could figure out which wire to splice into.

I've done this successfully on another car but I knew exactly which wire to splice into.  I've read several posts in a couple of forums, but I got confused about BCM's and interfaces and wasn't sure if I could just splice into a wire or if I had to run go back and connect to an interface.