String Compression

You are given a list of single-character strings chars. Compress it using run-length encoding and return the compressed list.

Scan chars from left to right and split it into runs of consecutive equal characters. For each run, in order:

• append the character once,
• if the run is longer than 1, append its length written as decimal digits, one digit per list entry (a run of 12 adds "1", "2").

A run of length 1 gets no count. Characters are compared exactly, so "a" and "A" are different. The same character can start a new run later if something else separates it.