Graduation
The sell-out buy turns the curve into a pool the program runs, with no way out.
When the eight hundred millionth coin is sold, the curve is finished. Graduation happens inside that same transaction.
What moves
The raise the curve collected and the two hundred million coins held back become the two sides of a pool. The price the pool opens at is the price the curve closed at, so there is no step change at the moment of graduation.
Where the liquidity goes
Into a pool this program runs itself, not an external venue.
There is no withdrawal instruction
The program exposes sixteen instructions. None of them removes liquidity from a graduated pool. The liquidity is not locked by a timer or by a promise; the code to take it out was never written.
Running the pool inside the program is also what keeps the rule intact. An external pool would trade at three in the morning like any other pool, and the coin's whole reason for existing would be gone the moment it graduated. Here, the pool keeps the exchange's hours exactly as the curve did, and the opening tax applies at every bell exactly as before.
After graduation
The coin page swaps its curve progress bar for the pool's reserves. Trading continues through the same buy and sell buttons, with the same fee, the same creator tax, the same hours.
The thing this cannot prevent
Anyone may create a separate pool for a graduated coin somewhere else, with no hours rule on it. Nothing on chain can stop that without restricting transfers, which would make the coin a worse token in every other way. What the program can promise is that the liquidity it locked lives only in the pool it runs, and that this site never routes anywhere else.