Basically, combat doesn't start until (A) one creature initiates an attack against another creature, or (B) a creature is anticipating an attack from another creature. You could sit in the "not yet in combat" zone for hours before you hit the moment of "just before combat."
I am not finding any rules to support this. The beginning of combat seems to be based on intent or perception of danger. At the time initiative is rolled, nobody has performed any actions yet, and nobody has committed to performing any actions yet. It seems that they are able to decide not only what they want to do, but also whether they want to act at all, as their turn comes up in the initiative. I don't see anything that would prohibit a character from delaying action in the surprise round, even if they are the only combatant that is not surprised.
I think the problem is that the rules concerning surprise are intended for group vs. group (or at least group vs. creature) combat, not for a 1 on 1 situation. The surprise rules work well when there are a number of people who can act during the surprise round, but not so well when there is one lonely rogue getting the drop on some poor sap who got stuck on the night shift (who is probably 3 days from retirement).
That being said, as a long-time GM, I would allow a rogue to do this in my game. It may be over-powered in a PvP type scenario, but a 1-on-1 surprise round just isn't a common occurrence, at least not in any game that I've run. I say, let the rogue have their fun once in a while, and put a construct on guard duty next time.