So, I think I want to make a him a hacker that never uses VR, as suggested. How do I go about making an AR hacker that specializes in infiltration, extraction, and avoiding detection? What skills and programs do I absolutely need? I need to specialize, rather than just being good at every aspect of being a hacker.
You'll want the logic-skill bonus augmentations from
Augmentation like PuSHeD, Encephleon, and Neocortical nanites. They help with hacking and hardware. They also make you better with first aid as well.
However, mundane hackers aren't specialists even on the matrix. Technomancers are what you want to be if you want to focus on the matrix. Mundane hacking is more about being competent hackers while doing other stuff. You may want to grab Cybercombat as that's the only thing Umaro's sample character doesn't do matrix wise. You could also get an agent for your own pwning.
If you're playing a more long-term game, I'll still use the Combat Hacker as a base. You may want to make him an ork so you can agility 9 eventually, but it'll cost more BP at start. You also could start off with rating 6 programs and System 6 which will "upgrade" once you buy a response 6 chip for your commlink. You could also drop the Restricted Gear, Born Rich, and the Suprathyroid + 5000Y to save 25 BP that can be spent on skills or attributes. That's definitely a "less power now for more power later" tradeoff though.
For a variation on sneaking mundane hacker, I do have my character I just built for my home Mission's game,
Dagon. He's a themed character so he may not be right for you. But he is built following more of a "power later" style. You may want to talk to your GM on how cyberlimbs and
Attitude's armor weaves work since it's very GM dependent and our group has discussed at length how we want to do it. There's also some +Swimming cheese, but seriously it's Swimming. I'm not sure if I'm ever going to roll it.