does miner program contains 'yes' or 'no' about this decision?
No. Forks are not votes, especially user activated forks. A user activated fork occurs with no requirements on miners. There is no signaling of readiness from miners nor do miners have any say on when it activates. All miners can do is decide whether they want to mine the fork and enforce its rules after the fork occurs.
Who is the representative in the working blockchain that inform 'this feature will be added!'? How is the notification received by all nodes?
There is no representative (that would imply there is some central authority in charge of the blockchain and there is not) nor is there any sort of notification system.
A user activated fork happens when a group of users decide they want some consensus change to occur. They write software that implements this change along with the activation time. Those users will then try to get other users to join them. When their fork activates, they will start enforcing their new rules.