Implement `merge_weekly_intervals(intervals)`. Each interval is `[start_day, start_time, end_day, end_time]`. Days are `Mon`, `Tue`, `Wed`, `Thu`, `Fri`, `Sat`, or `Sun`. Times use 24-hour `HH:MM`. Intervals are closed, never wrap from Sunday into the next week, and satisfy start at or before end. Return merged intervals in the same representation, sorted by start. Intervals that overlap or share an endpoint must merge. ### Constraints - `0 <= len(intervals) <= 200000` - Times range from `00:00` through `23:59`. - Input may be unsorted and contain duplicates. ### Example `[["Mon","09:00","Mon","17:00"], ["Mon","17:00","Tue","10:00"], ["Wed","12:00","Wed","13:00"]]` returns `[["Mon","09:00","Tue","10:00"], ["Wed","12:00","Wed","13:00"]]`. ```hint Normalize before merging Convert each day and time to an integer minute offset from Monday, then apply the closed-interval merge rule. ``` ```hint Format only after the algorithm Keeping parsing and formatting separate from interval logic makes boundary tests easier. ```