"Have I broken the law?" is a tricky question. You have, by the strictest letter of the law, engaged in an activity that could be deemed grounds for deportation and/or future denials of the visa. But by the same interpretation ~100% of visitors in the country are breaking the law and violating the terms of their visas in some way. So unless you yourself go to an immigration officer and say "I intend to engage in an illegal activity please deny me entry" you will be fine.
Immigration officers will ask your purpose of stay, and if your answer is not clear and they start questioning in more detail and you blurt out you're gonna do something which is technically not allowed by your visa, then you have a problem. Comparing yourself with others who also do illegal things during their stay won't help you then.
Your purpose is to attend xyz conference. That's literally all you have to say. I can assure you "what are you going to be doing between the hours of 6pm to 8pm on Tuesday when you have a break, and will you be commiting any code at that time?" is not going to come up.
Sure. Mentioning anything more than that will lead to trouble. But many people are not aware of how thin the line is and mention they are also going to work remote for a few hours. Or meet with colleagues for a hacking session. That's already too much.
"Have I broken the law?" is a tricky question. You have, by the strictest letter of the law, engaged in an activity that could be deemed grounds for deportation and/or future denials of the visa. But by the same interpretation ~100% of visitors in the country are breaking the law and violating the terms of their visas in some way. So unless you yourself go to an immigration officer and say "I intend to engage in an illegal activity please deny me entry" you will be fine.