Shift grants with promotions that start next entry

Track workers clocking in and out, apply promotions starting from the next office entry, and total granted bonuses across overlapping work sessions.

• Level 1: add_worker(id, position, rate), register(id, ts) toggles in and out, get_time(id) totals finished sessions.
• Level 2: top_workers(n, position) as "id(time)", counting time worked in that position.
• Level 3: promote(id, position, rate, start_ts) takes effect at the first entry at or after start_ts; pay(id, start, end).
• Level 4: add_bonus_window(start, end): time inside any window is paid double (never more, even where windows overlap).

class Office:
    def add_worker(self, worker_id, position, rate): ...
    def register(self, worker_id, ts): ...
    def get_time(self, worker_id): ...

    def top_workers(self, n, position): ...

    def promote(self, worker_id, position, rate, start_ts): ...
    def pay(self, worker_id, start, end): ...

    def add_bonus_window(self, start, end): ...