-----Description----- 
This task requires writing a Lean 4 method that identifies the first repeated character in a given string. The method should return a tuple containing a Boolean value and a character. The Boolean value indicates whether any character in the string is repeated. If it is true, the accompanying character is the first character that appears more than once. If it is false, it indicates that there are no repeated characters in the string.

-----Input-----
The input consists of:
s: A string.

-----Output-----
The output is a tuple (Bool × Char):
- Returns true and the first repeated character in the string if any repeated character is found.
- Returns false and an arbitrary character if no repeated characters are present.

-----Note-----
There are no preconditions; the method is expected to work for any non-null string.