Part 3: Mechanics: Continuation of the above
Oh yeah I know how to reduce unhappiness, it was a question of whether it's possible to stop the city rioting every time that new citizen is added. I think I'm misremembering, maybe it was a Civ 3 thing. Good general write-up though!
Oh, sorry, I misunderstood the question.
The answer is technically yes. The city will go into disorder at the same instant that it grows and you will then get a notification about it. If you're a Democracy, you must then fix the problem right that turn or your government will collapse into Anarchy and everything will be ruined everywhere forever.
If you manually check every city every turn (which you should do), you can notice when the city's Food box has reached the max (note that the city never grows until the turn after the box maxes). Depending on the exact circumstances, it may be possible to employ some kind of happiness-boosting measure (like turning your only citizen into an Entertainer or building a Temple or whatever) right that turn. Then when your city grows, it already has the Entertainer, so it doesn't go into disorder. This doesn't really make much of a difference though since you've just gone from 1 turn of producing nothing due to civil disorder to 1 turn of producing almost nothing since your only productive citizen was turned into a useless Entertainer.